<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019eb852-dae2-729a-8285-fdc2a5415010,g:ab798e18-6704-4a2b-9f4f-3d6a80952cd9-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/CoverPage" xlink:type="simple" xlink:href="ago-20260630.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019eb852-df6a-768e-9c73-9125f704e98f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntitiesTable_019eb852-df6a-768e-9c73-9125f704e98f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsExchangeAxis_019eb852-df6a-7a3e-a6b5-038fc46c591f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingsExchangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019eb852-df6a-768e-9c73-9125f704e98f" xlink:to="loc_dei_EntityListingsExchangeAxis_019eb852-df6a-7a3e-a6b5-038fc46c591f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_019eb852-df6a-7a3e-a6b5-038fc46c591f_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_EntityListingsExchangeAxis_019eb852-df6a-7a3e-a6b5-038fc46c591f" xlink:to="loc_dei_ExchangeDomain_019eb852-df6a-7a3e-a6b5-038fc46c591f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_019eb852-df6a-79fe-9092-062520c87e39" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_EntityListingsExchangeAxis_019eb852-df6a-7a3e-a6b5-038fc46c591f" xlink:to="loc_dei_ExchangeDomain_019eb852-df6a-79fe-9092-062520c87e39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_exch_XNYS_019eb852-df6a-7b2e-9533-64ee325ed40a" xlink:href="https://xbrl.sec.gov/exch/2026/exch-2026.xsd#exch_XNYS"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_ExchangeDomain_019eb852-df6a-79fe-9092-062520c87e39" xlink:to="loc_exch_XNYS_019eb852-df6a-7b2e-9533-64ee325ed40a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019eb852-df6a-777b-811d-0e07c214b784" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019eb852-df6a-768e-9c73-9125f704e98f" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019eb852-df6a-777b-811d-0e07c214b784" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-777b-811d-0e07c214b784_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019eb852-df6a-777b-811d-0e07c214b784" xlink:to="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-777b-811d-0e07c214b784_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-7754-88a7-b68905c4f1b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019eb852-df6a-777b-811d-0e07c214b784" xlink:to="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-7754-88a7-b68905c4f1b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019eb852-df6a-74fa-b5a5-fe8140fd9abf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-7754-88a7-b68905c4f1b0" xlink:to="loc_us-gaap_CommonStockMember_019eb852-df6a-74fa-b5a5-fe8140fd9abf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyUSHoldingsInc6125SeniorNotesDue2028Member_019eb852-df6a-780f-9120-372f80a9ea76" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyUSHoldingsInc6125SeniorNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-7754-88a7-b68905c4f1b0" xlink:to="loc_ago_AssuredGuarantyUSHoldingsInc6125SeniorNotesDue2028Member_019eb852-df6a-780f-9120-372f80a9ea76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyUSHoldingsInc3150SeniorNotesDue2031Member_019eb852-df6a-72f6-ab03-40b90df81b28" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyUSHoldingsInc3150SeniorNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-7754-88a7-b68905c4f1b0" xlink:to="loc_ago_AssuredGuarantyUSHoldingsInc3150SeniorNotesDue2031Member_019eb852-df6a-72f6-ab03-40b90df81b28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyUSHoldingsInc3600SeniorNotesDue2051Member_019eb852-df6a-7a80-89cd-0f5ee1e8efa0" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyUSHoldingsInc3600SeniorNotesDue2051Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019eb852-df6a-7754-88a7-b68905c4f1b0" xlink:to="loc_ago_AssuredGuarantyUSHoldingsInc3600SeniorNotesDue2051Member_019eb852-df6a-7a80-89cd-0f5ee1e8efa0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019eb852-df6a-7c7d-af79-0a17f0da9d09" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_DocumentType_019eb852-df6a-7c7d-af79-0a17f0da9d09" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019eb852-df6a-708e-a492-8e08de6ba546" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_DocumentQuarterlyReport_019eb852-df6a-708e-a492-8e08de6ba546" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019eb852-df6a-773f-9932-984e6344001d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_DocumentPeriodEndDate_019eb852-df6a-773f-9932-984e6344001d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019eb852-df6a-7914-bc12-465fa8ff8a65" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_DocumentTransitionReport_019eb852-df6a-7914-bc12-465fa8ff8a65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019eb852-df6a-7329-86be-c7fff54de388" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityFileNumber_019eb852-df6a-7329-86be-c7fff54de388" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019eb852-df6a-7cc0-93a3-65d161428033" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityRegistrantName_019eb852-df6a-7cc0-93a3-65d161428033" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019eb852-df6a-7026-99d9-85bfea3aa22f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019eb852-df6a-7026-99d9-85bfea3aa22f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019eb852-df6a-7ae4-beda-d2e7c1362fc6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityTaxIdentificationNumber_019eb852-df6a-7ae4-beda-d2e7c1362fc6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019eb852-df6a-7a99-a0f4-58383d72b160" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityAddressAddressLine1_019eb852-df6a-7a99-a0f4-58383d72b160" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019eb852-df6a-7c34-bd34-4c853976949b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityAddressCityOrTown_019eb852-df6a-7c34-bd34-4c853976949b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019eb852-df6a-7378-a577-7fe32e4efb39" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityAddressPostalZipCode_019eb852-df6a-7378-a577-7fe32e4efb39" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCountry_019eb852-df6a-7563-bc30-453ca3a83b12" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCountry"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityAddressCountry_019eb852-df6a-7563-bc30-453ca3a83b12" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019eb852-df6a-73ae-9f03-85776d078771" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_CityAreaCode_019eb852-df6a-73ae-9f03-85776d078771" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019eb852-df6a-7ab5-b86d-50417baa40ac" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_LocalPhoneNumber_019eb852-df6a-7ab5-b86d-50417baa40ac" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019eb852-df6a-7015-acaa-5047df81f929" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_Security12bTitle_019eb852-df6a-7015-acaa-5047df81f929" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019eb852-df6a-7ec5-b092-2176a85c103c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_TradingSymbol_019eb852-df6a-7ec5-b092-2176a85c103c" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019eb852-df6a-766e-9392-91e1341f54a5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_SecurityExchangeName_019eb852-df6a-766e-9392-91e1341f54a5" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019eb852-df6a-7be2-8f9d-4349e674b7f7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityCurrentReportingStatus_019eb852-df6a-7be2-8f9d-4349e674b7f7" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019eb852-df6a-7fe4-9a0a-1b4947f9dccd" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityInteractiveDataCurrent_019eb852-df6a-7fe4-9a0a-1b4947f9dccd" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019eb852-df6a-7235-95b3-3b2d367eefd8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityFilerCategory_019eb852-df6a-7235-95b3-3b2d367eefd8" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019eb852-df6a-7724-b725-a47243247b46" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntitySmallBusiness_019eb852-df6a-7724-b725-a47243247b46" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019eb852-df6a-798e-8ca6-5703e9583451" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityEmergingGrowthCompany_019eb852-df6a-798e-8ca6-5703e9583451" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019eb852-df6a-7fd9-93ca-761108decf47" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityShellCompany_019eb852-df6a-7fd9-93ca-761108decf47" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019eb852-df6a-7458-a7dc-3c29e1df685e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019eb852-df6a-7458-a7dc-3c29e1df685e" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019eb852-df6a-7879-b142-5c008bc6a7c6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_EntityCentralIndexKey_019eb852-df6a-7879-b142-5c008bc6a7c6" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019eb852-df6a-7c6f-8eb8-b10bda529d59" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_AmendmentFlag_019eb852-df6a-7c6f-8eb8-b10bda529d59" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019eb852-df6a-753f-87ea-3b89370e53b0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_CurrentFiscalYearEndDate_019eb852-df6a-753f-87ea-3b89370e53b0" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019eb852-df6a-7f31-abf5-c9cdb2ce8dce" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_DocumentFiscalYearFocus_019eb852-df6a-7f31-abf5-c9cdb2ce8dce" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019eb852-df6a-7c51-904c-8038fa382f62" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019eb852-df6a-7b5f-a30a-23f0103636ea" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019eb852-df6a-7c51-904c-8038fa382f62" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/CondensedConsolidatedStatementsofShareholdersEquityUnaudited" xlink:type="simple" xlink:href="ago-20260630.xsd#CondensedConsolidatedStatementsofShareholdersEquityUnaudited"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/CondensedConsolidatedStatementsofShareholdersEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019eb852-df6b-79f0-9857-49c84e05cc17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019eb852-df6b-72bb-a9bf-64142e1744e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019eb852-df6b-79f0-9857-49c84e05cc17" xlink:to="loc_us-gaap_StatementTable_019eb852-df6b-72bb-a9bf-64142e1744e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019eb852-df6b-758f-be91-33fcc80135ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019eb852-df6b-72bb-a9bf-64142e1744e4" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019eb852-df6b-758f-be91-33fcc80135ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-df6b-758f-be91-33fcc80135ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-df6b-758f-be91-33fcc80135ab" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-df6b-758f-be91-33fcc80135ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-df6b-7a7b-b437-20d4bd2828c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-df6b-758f-be91-33fcc80135ab" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-df6b-7a7b-b437-20d4bd2828c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParentMember_019eb852-df6b-7c9e-9e6f-577cc5007e40" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb852-df6b-7a7b-b437-20d4bd2828c7" xlink:to="loc_us-gaap_ParentMember_019eb852-df6b-7c9e-9e6f-577cc5007e40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019eb852-df6b-798c-85f0-21d413ba2e27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019eb852-df6b-7c9e-9e6f-577cc5007e40" xlink:to="loc_us-gaap_CommonStockMember_019eb852-df6b-798c-85f0-21d413ba2e27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019eb852-df6b-7168-bfa1-1811d656b6af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019eb852-df6b-7c9e-9e6f-577cc5007e40" xlink:to="loc_us-gaap_RetainedEarningsMember_019eb852-df6b-7168-bfa1-1811d656b6af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-df6b-7905-98df-077dcc1dc371" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019eb852-df6b-7c9e-9e6f-577cc5007e40" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-df6b-7905-98df-077dcc1dc371" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationShareBasedPaymentsMember_019eb852-df6b-7a12-a452-27ff02d85f68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCompensationShareBasedPaymentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019eb852-df6b-7c9e-9e6f-577cc5007e40" xlink:to="loc_us-gaap_DeferredCompensationShareBasedPaymentsMember_019eb852-df6b-7a12-a452-27ff02d85f68" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019eb852-df6b-7ffb-9091-8522c5871ba0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb852-df6b-7a7b-b437-20d4bd2828c7" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019eb852-df6b-7ffb-9091-8522c5871ba0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019eb852-df6b-79f0-9857-49c84e05cc17" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_019eb852-df6b-70ee-a19d-2e9b8c1d0112" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_SharesOutstanding_019eb852-df6b-70ee-a19d-2e9b8c1d0112" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-df6b-7c0e-9e5b-77aa6e07264e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-df6b-7c0e-9e5b-77aa6e07264e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_019eb852-df6b-7fcf-87e3-73da96ae1e23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_019eb852-df6b-7fcf-87e3-73da96ae1e23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_019eb852-df6b-7e5a-9027-97902f8d9f3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_DividendsCommonStockCash_019eb852-df6b-7e5a-9027-97902f8d9f3f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_NoncontrollingInterestIncreaseFromVIEConsolidation_019f18c9-aba0-7798-940b-7f22d7079abf" xlink:href="ago-20260630.xsd#ago_NoncontrollingInterestIncreaseFromVIEConsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_ago_NoncontrollingInterestIncreaseFromVIEConsolidation_019f18c9-aba0-7798-940b-7f22d7079abf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019eb852-df6b-76f4-97ea-37525515daa6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019eb852-df6b-76f4-97ea-37525515daa6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019eb852-df6b-7dac-afaa-f79cbab695ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019eb852-df6b-7dac-afaa-f79cbab695ea" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_StockIssuedDuringPeriodSharesShareBasedCompensationAndOther_019eb852-df6b-7de5-8169-2f5fc9208f0e" xlink:href="ago-20260630.xsd#ago_StockIssuedDuringPeriodSharesShareBasedCompensationAndOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_ago_StockIssuedDuringPeriodSharesShareBasedCompensationAndOther_019eb852-df6b-7de5-8169-2f5fc9208f0e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_StockIssuedDuringPeriodValueSharebasedCompensationandOther_019eb852-df6b-721c-8126-1defcf47bd91" xlink:href="ago-20260630.xsd#ago_StockIssuedDuringPeriodValueSharebasedCompensationandOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_ago_StockIssuedDuringPeriodValueSharebasedCompensationandOther_019eb852-df6b-721c-8126-1defcf47bd91" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019eb852-df6b-7282-b06b-567d0ed20cf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019eb852-df6b-7282-b06b-567d0ed20cf5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation_019eb852-df6b-70f7-8480-9f45a87b28d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation_019eb852-df6b-70f7-8480-9f45a87b28d1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb852-df6b-73e9-85fb-49bc78cbcee9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb852-df6b-7626-8908-16e46e52c79d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb852-df6b-73e9-85fb-49bc78cbcee9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_019eb852-df6b-72db-b10c-343f06a97715" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-df6b-7281-af9f-3d92360405c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/BusinessandBasisofPresentationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#BusinessandBasisofPresentationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/BusinessandBasisofPresentationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019eb852-df6b-7673-8e90-8cabc0b9012c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongLivedAssetsHeldForSaleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019eb852-df6b-7332-922b-f7236b144c95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019eb852-df6b-7673-8e90-8cabc0b9012c" xlink:to="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019eb852-df6b-7332-922b-f7236b144c95" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-df6b-7a10-9de8-262d7320649e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019eb852-df6b-7332-922b-f7236b144c95" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-df6b-7a10-9de8-262d7320649e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019eb852-df6b-7a10-9de8-262d7320649e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-df6b-7a10-9de8-262d7320649e" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019eb852-df6b-7a10-9de8-262d7320649e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019eb852-df6b-78d0-8bac-8af9087538a1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-df6b-7a10-9de8-262d7320649e" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019eb852-df6b-78d0-8bac-8af9087538a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SoundPointCapitalManagementLPMember_019eb852-df6b-7a03-8f5a-f81adda2d90a" xlink:href="ago-20260630.xsd#ago_SoundPointCapitalManagementLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019eb852-df6b-78d0-8bac-8af9087538a1" xlink:to="loc_ago_SoundPointCapitalManagementLPMember_019eb852-df6b-7a03-8f5a-f81adda2d90a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-70bb-8875-68d51019ece6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019eb852-df6b-7332-922b-f7236b144c95" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-70bb-8875-68d51019ece6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-70bb-8875-68d51019ece6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-70bb-8875-68d51019ece6" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-70bb-8875-68d51019ece6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-7e69-8bf9-067b61800695" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-70bb-8875-68d51019ece6" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-7e69-8bf9-067b61800695" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-72b0-b30f-474e6db3d209" xlink:href="ago-20260630.xsd#ago_AssuredLifeReAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-7e69-8bf9-067b61800695" xlink:to="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-72b0-b30f-474e6db3d209" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019eb852-df6b-7daa-8f85-07017d02571a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019eb852-df6b-7673-8e90-8cabc0b9012c" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019eb852-df6b-7daa-8f85-07017d02571a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ReinsuranceNumberOfBusinessesReinsured_019eb852-df6b-7232-9bd9-97217cff6c2b" xlink:href="ago-20260630.xsd#ago_ReinsuranceNumberOfBusinessesReinsured"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019eb852-df6b-7673-8e90-8cabc0b9012c" xlink:to="loc_ago_ReinsuranceNumberOfBusinessesReinsured_019eb852-df6b-7232-9bd9-97217cff6c2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssetManagementOwnershipInterest_019eb852-df6b-7c72-8e07-0b75ff50b201" xlink:href="ago-20260630.xsd#ago_AssetManagementOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019eb852-df6b-7673-8e90-8cabc0b9012c" xlink:to="loc_ago_AssetManagementOwnershipInterest_019eb852-df6b-7c72-8e07-0b75ff50b201" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_HoldingCompanieswithOutstandingPublicDebtNumber_019eb852-df6b-7088-bf08-8c66872b37e7" xlink:href="ago-20260630.xsd#ago_HoldingCompanieswithOutstandingPublicDebtNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019eb852-df6b-7673-8e90-8cabc0b9012c" xlink:to="loc_ago_HoldingCompanieswithOutstandingPublicDebtNumber_019eb852-df6b-7088-bf08-8c66872b37e7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/AssuredLifeReAcquisitionAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#AssuredLifeReAcquisitionAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/AssuredLifeReAcquisitionAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-73de-83f8-201b82459eb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-73de-83f8-201b82459eb7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-72fe-a2f5-c5ad23f32d33" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-73de-83f8-201b82459eb7" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-72fe-a2f5-c5ad23f32d33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-72fe-a2f5-c5ad23f32d33_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-72fe-a2f5-c5ad23f32d33" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-72fe-a2f5-c5ad23f32d33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-77ed-a424-eeb5821e8f32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-72fe-a2f5-c5ad23f32d33" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-77ed-a424-eeb5821e8f32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-78d2-abb7-d1faca7fbaf0" xlink:href="ago-20260630.xsd#ago_AssuredLifeReAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-77ed-a424-eeb5821e8f32" xlink:to="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-78d2-abb7-d1faca7fbaf0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredLifeReAcquisitionPensionRiskTransfersMember_019eb852-df6b-79cf-88d3-c63e37260c00" xlink:href="ago-20260630.xsd#ago_AssuredLifeReAcquisitionPensionRiskTransfersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-78d2-abb7-d1faca7fbaf0" xlink:to="loc_ago_AssuredLifeReAcquisitionPensionRiskTransfersMember_019eb852-df6b-79cf-88d3-c63e37260c00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredLifeReAcquisitionMultiYearGuaranteedAnnuitiesMember_019eb852-df6b-7d62-a4c0-2acce13e901f" xlink:href="ago-20260630.xsd#ago_AssuredLifeReAcquisitionMultiYearGuaranteedAnnuitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-78d2-abb7-d1faca7fbaf0" xlink:to="loc_ago_AssuredLifeReAcquisitionMultiYearGuaranteedAnnuitiesMember_019eb852-df6b-7d62-a4c0-2acce13e901f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019eb852-df6b-7f01-ba01-ea3997351f6d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-73de-83f8-201b82459eb7" xlink:to="loc_dei_LegalEntityAxis_019eb852-df6b-7f01-ba01-ea3997351f6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-df6b-7f01-ba01-ea3997351f6d_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019eb852-df6b-7f01-ba01-ea3997351f6d" xlink:to="loc_dei_EntityDomain_019eb852-df6b-7f01-ba01-ea3997351f6d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-df6b-78e2-9d83-c9dd5c897aa4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019eb852-df6b-7f01-ba01-ea3997351f6d" xlink:to="loc_dei_EntityDomain_019eb852-df6b-78e2-9d83-c9dd5c897aa4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyReLtd.Member_019eb852-df6b-7865-88bf-27346662d3f4" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyReLtd.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019eb852-df6b-78e2-9d83-c9dd5c897aa4" xlink:to="loc_ago_AssuredGuarantyReLtd.Member_019eb852-df6b-7865-88bf-27346662d3f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-df6b-73de-b5fd-7aa321b9b4b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-73de-83f8-201b82459eb7" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-df6b-73de-b5fd-7aa321b9b4b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-df6b-73de-b5fd-7aa321b9b4b8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-df6b-73de-b5fd-7aa321b9b4b8" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-df6b-73de-b5fd-7aa321b9b4b8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-df6b-7d15-b9ba-7229bdcfab8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-df6b-73de-b5fd-7aa321b9b4b8" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-df6b-7d15-b9ba-7229bdcfab8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PensionRiskTransfersInsuranceLiabilitiesMember_019eb852-df6b-7c01-aa5d-1abc10a2ca19" xlink:href="ago-20260630.xsd#ago_PensionRiskTransfersInsuranceLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-df6b-7d15-b9ba-7229bdcfab8f" xlink:to="loc_ago_PensionRiskTransfersInsuranceLiabilitiesMember_019eb852-df6b-7c01-aa5d-1abc10a2ca19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MultiYearGuaranteedAnnuityPolicyholderBalancesMember_019eb852-df6b-7ce3-bdad-8757aabfac28" xlink:href="ago-20260630.xsd#ago_MultiYearGuaranteedAnnuityPolicyholderBalancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-df6b-7d15-b9ba-7229bdcfab8f" xlink:to="loc_ago_MultiYearGuaranteedAnnuityPolicyholderBalancesMember_019eb852-df6b-7ce3-bdad-8757aabfac28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesByJurisdictionAxis_019eb852-df6b-7e50-8a68-9440fbdbbab1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatutoryAccountingPracticesByJurisdictionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-73de-83f8-201b82459eb7" xlink:to="loc_us-gaap_StatutoryAccountingPracticesByJurisdictionAxis_019eb852-df6b-7e50-8a68-9440fbdbbab1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesJurisdictionDomain_019eb852-df6b-7e50-8a68-9440fbdbbab1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatutoryAccountingPracticesJurisdictionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatutoryAccountingPracticesByJurisdictionAxis_019eb852-df6b-7e50-8a68-9440fbdbbab1" xlink:to="loc_us-gaap_StatutoryAccountingPracticesJurisdictionDomain_019eb852-df6b-7e50-8a68-9440fbdbbab1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesJurisdictionDomain_019eb852-df6b-76de-bbee-667e008a7eda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatutoryAccountingPracticesJurisdictionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatutoryAccountingPracticesByJurisdictionAxis_019eb852-df6b-7e50-8a68-9440fbdbbab1" xlink:to="loc_us-gaap_StatutoryAccountingPracticesJurisdictionDomain_019eb852-df6b-76de-bbee-667e008a7eda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_BM_019eb852-df6b-7306-8ed4-3c46a380d647" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_BM"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatutoryAccountingPracticesJurisdictionDomain_019eb852-df6b-76de-bbee-667e008a7eda" xlink:to="loc_country_BM_019eb852-df6b-7306-8ed4-3c46a380d647" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019eb852-df6b-7487-9325-1217aa326c69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019eb852-df6b-7487-9325-1217aa326c69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019eb852-df6b-78a7-96b1-014e3d33941b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019eb852-df6b-78a7-96b1-014e3d33941b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationValueOfBusinessAcquired_019eb852-df6b-74ea-a5d7-564b0fd94918" xlink:href="ago-20260630.xsd#ago_BusinessCombinationValueOfBusinessAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_ago_BusinessCombinationValueOfBusinessAcquired_019eb852-df6b-74ea-a5d7-564b0fd94918" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AcquiredAssetsWeightedAverageUsefulLife_019eb852-df6b-7601-a800-ac0a39a20468" xlink:href="ago-20260630.xsd#ago_AcquiredAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_ago_AcquiredAssetsWeightedAverageUsefulLife_019eb852-df6b-7601-a800-ac0a39a20468" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019eb852-df6b-7f80-be3c-a5218d5c69d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019eb852-df6b-7f80-be3c-a5218d5c69d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_019eb852-df6b-7527-ace6-508352ac2560" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_019eb852-df6b-7527-ace6-508352ac2560" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019eb852-df6b-7441-a0da-bed4f5c8ddd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019eb852-df6b-7441-a0da-bed4f5c8ddd6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_019eb852-df6b-79c9-8344-b6dbc186cbe7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_019eb852-df6b-79c9-8344-b6dbc186cbe7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_019eb852-df6b-770c-b64e-e0dd5c5ce685" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_019eb852-df6b-770c-b64e-e0dd5c5ce685" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DividendPaymentRestrictionsSchedulePercentageOfStatutoryCapitalAndSurplus_019eb852-df6b-7997-852b-46ae27dce47e" xlink:href="ago-20260630.xsd#ago_DividendPaymentRestrictionsSchedulePercentageOfStatutoryCapitalAndSurplus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_ago_DividendPaymentRestrictionsSchedulePercentageOfStatutoryCapitalAndSurplus_019eb852-df6b-7997-852b-46ae27dce47e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval_019eb852-df6b-7da9-8b28-1d352ac0b39c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval_019eb852-df6b-7da9-8b28-1d352ac0b39c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_UnencumberedAsset_019eb852-df6b-7bd4-8c7d-92e124516c20" xlink:href="ago-20260630.xsd#ago_UnencumberedAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_ago_UnencumberedAsset_019eb852-df6b-7bd4-8c7d-92e124516c20" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DividendPaymentRestrictionsScheduleAmountOfStatutoryCapital_019eb852-df6b-72c5-8f6f-898c6eef0ae4" xlink:href="ago-20260630.xsd#ago_DividendPaymentRestrictionsScheduleAmountOfStatutoryCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7d00-abfc-df88d8883b23" xlink:to="loc_ago_DividendPaymentRestrictionsScheduleAmountOfStatutoryCapital_019eb852-df6b-72c5-8f6f-898c6eef0ae4" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/AssuredLifeReAcquisitionNetEffectoftheAcquisitionontheAcquisitionDateDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#AssuredLifeReAcquisitionNetEffectoftheAcquisitionontheAcquisitionDateDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/AssuredLifeReAcquisitionNetEffectoftheAcquisitionontheAcquisitionDateDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-7768-a9bd-5afc7acd5d95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-7768-a9bd-5afc7acd5d95" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-709a-8105-046fb5737d24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019eb852-df6b-7768-a9bd-5afc7acd5d95" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-709a-8105-046fb5737d24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-709a-8105-046fb5737d24_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-709a-8105-046fb5737d24" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-709a-8105-046fb5737d24_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-781b-9f4d-728f41ba61df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019eb852-df6b-709a-8105-046fb5737d24" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-781b-9f4d-728f41ba61df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-766b-a452-eb502951a6e6" xlink:href="ago-20260630.xsd#ago_AssuredLifeReAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019eb852-df6b-781b-9f4d-728f41ba61df" xlink:to="loc_ago_AssuredLifeReAcquisitionMember_019eb852-df6b-766b-a452-eb502951a6e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019eb852-df6b-7d1a-818b-9399d1ae452b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019eb852-df6b-7d1a-818b-9399d1ae452b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationRecognizedAssetAcquiredInvestments_019eb852-df6b-7c98-b316-702cd051d280" xlink:href="ago-20260630.xsd#ago_BusinessCombinationRecognizedAssetAcquiredInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:to="loc_ago_BusinessCombinationRecognizedAssetAcquiredInvestments_019eb852-df6b-7c98-b316-702cd051d280" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019eb852-df6b-7dc7-a07a-ddccfd3581f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019eb852-df6b-7dc7-a07a-ddccfd3581f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationRecognizedAssetAcquiredFundsWithheld_019eb852-df6b-713e-ba77-19327cc3cf9c" xlink:href="ago-20260630.xsd#ago_BusinessCombinationRecognizedAssetAcquiredFundsWithheld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:to="loc_ago_BusinessCombinationRecognizedAssetAcquiredFundsWithheld_019eb852-df6b-713e-ba77-19327cc3cf9c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationRecognizedAssetAcquiredOtherAsset_019eb852-df6b-70bd-8c23-9480f5a2cb1c" xlink:href="ago-20260630.xsd#ago_BusinessCombinationRecognizedAssetAcquiredOtherAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:to="loc_ago_BusinessCombinationRecognizedAssetAcquiredOtherAsset_019eb852-df6b-70bd-8c23-9480f5a2cb1c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019eb852-df6b-79d2-984f-f2030efef7c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019eb852-df6b-70a7-96b3-21f76b8f694c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019eb852-df6b-79d2-984f-f2030efef7c6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019eb852-df6b-7df1-b797-af839770aa35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019eb852-df6b-7df1-b797-af839770aa35" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationRecognizedLiabilityAssumedFuturePolicyBenefits_019eb852-df6b-7d58-bafc-f51a4e93a908" xlink:href="ago-20260630.xsd#ago_BusinessCombinationRecognizedLiabilityAssumedFuturePolicyBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019eb852-df6b-7df1-b797-af839770aa35" xlink:to="loc_ago_BusinessCombinationRecognizedLiabilityAssumedFuturePolicyBenefits_019eb852-df6b-7d58-bafc-f51a4e93a908" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationRecognizedLiabilityAssumedPolicyholderAccountBalances_019eb852-df6b-7202-b638-56c4b217e6a0" xlink:href="ago-20260630.xsd#ago_BusinessCombinationRecognizedLiabilityAssumedPolicyholderAccountBalances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019eb852-df6b-7df1-b797-af839770aa35" xlink:to="loc_ago_BusinessCombinationRecognizedLiabilityAssumedPolicyholderAccountBalances_019eb852-df6b-7202-b638-56c4b217e6a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BusinessCombinationRecognizedLiabilityAssumedOtherLiability_019eb852-df6b-7a56-a272-779bd2d3c149" xlink:href="ago-20260630.xsd#ago_BusinessCombinationRecognizedLiabilityAssumedOtherLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019eb852-df6b-7df1-b797-af839770aa35" xlink:to="loc_ago_BusinessCombinationRecognizedLiabilityAssumedOtherLiability_019eb852-df6b-7a56-a272-779bd2d3c149" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019eb852-df6b-739d-b80e-6e9cf25e2197" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019eb852-df6b-7df1-b797-af839770aa35" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019eb852-df6b-739d-b80e-6e9cf25e2197" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019eb852-df6b-7edd-a52d-108d8c9e7e7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019eb852-df6b-7edd-a52d-108d8c9e7e7b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount_019eb852-df6b-7969-87a7-63d5f8d90fb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019eb852-df6b-7770-95f9-d14d1e44c52b" xlink:to="loc_us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount_019eb852-df6b-7969-87a7-63d5f8d90fb6" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/SegmentInformationAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#SegmentInformationAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/SegmentInformationAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-749b-8d59-98d19b48dcc5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-78b3-b892-88e725a3466b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-749b-8d59-98d19b48dcc5" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-78b3-b892-88e725a3466b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7bea-8b59-fc672353c566" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-78b3-b892-88e725a3466b" xlink:to="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7bea-8b59-fc672353c566" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7bea-8b59-fc672353c566_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7bea-8b59-fc672353c566" xlink:to="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7bea-8b59-fc672353c566_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019eb852-df6b-76ca-b3aa-185b0477ca28" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7bea-8b59-fc672353c566" xlink:to="loc_srt_ConsolidationItemsDomain_019eb852-df6b-76ca-b3aa-185b0477ca28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019eb852-df6b-77db-8dfe-6dde179a976d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-76ca-b3aa-185b0477ca28" xlink:to="loc_us-gaap_OperatingSegmentsMember_019eb852-df6b-77db-8dfe-6dde179a976d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7669-94ee-c756b908fef3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-78b3-b892-88e725a3466b" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7669-94ee-c756b908fef3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019eb852-df6b-7669-94ee-c756b908fef3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7669-94ee-c756b908fef3" xlink:to="loc_us-gaap_SegmentDomain_019eb852-df6b-7669-94ee-c756b908fef3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019eb852-df6b-75ff-8146-cfe493e3103b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7669-94ee-c756b908fef3" xlink:to="loc_us-gaap_SegmentDomain_019eb852-df6b-75ff-8146-cfe493e3103b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssetManagementSegmentMember_019eb852-df6b-7839-89d2-7f044eaeb78c" xlink:href="ago-20260630.xsd#ago_AssetManagementSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-75ff-8146-cfe493e3103b" xlink:to="loc_ago_AssetManagementSegmentMember_019eb852-df6b-7839-89d2-7f044eaeb78c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_019eb852-df6b-7ec4-afed-a489e23c0498" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-749b-8d59-98d19b48dcc5" xlink:to="loc_us-gaap_NumberOfReportableSegments_019eb852-df6b-7ec4-afed-a489e23c0498" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019eb852-df6b-7c6b-8ae4-fc0b685a79da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-749b-8d59-98d19b48dcc5" xlink:to="loc_us-gaap_Revenues_019eb852-df6b-7c6b-8ae4-fc0b685a79da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BenefitsLossesAndExpenses_019eb852-df6b-7d74-9fb9-07942ee12624" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BenefitsLossesAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-749b-8d59-98d19b48dcc5" xlink:to="loc_us-gaap_BenefitsLossesAndExpenses_019eb852-df6b-7d74-9fb9-07942ee12624" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/SegmentInformationSegmentInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#SegmentInformationSegmentInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/SegmentInformationSegmentInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7f9c-81cf-4dcde7a1bc0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7f9c-81cf-4dcde7a1bc0a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7ad2-b6fc-0f8896fd71fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7f9c-81cf-4dcde7a1bc0a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7ad2-b6fc-0f8896fd71fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019eb852-df6b-7ad2-b6fc-0f8896fd71fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7ad2-b6fc-0f8896fd71fa" xlink:to="loc_us-gaap_SegmentDomain_019eb852-df6b-7ad2-b6fc-0f8896fd71fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019eb852-df6b-7827-b82f-a3f9938d54a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7ad2-b6fc-0f8896fd71fa" xlink:to="loc_us-gaap_SegmentDomain_019eb852-df6b-7827-b82f-a3f9938d54a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantySegmentMember_019eb852-df6b-746b-92a9-89332301d67a" xlink:href="ago-20260630.xsd#ago_FinancialGuarantySegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-7827-b82f-a3f9938d54a8" xlink:to="loc_ago_FinancialGuarantySegmentMember_019eb852-df6b-746b-92a9-89332301d67a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AnnuityReinsuranceSegmentMember_019eb852-df6b-77db-bdf7-c536187492af" xlink:href="ago-20260630.xsd#ago_AnnuityReinsuranceSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-7827-b82f-a3f9938d54a8" xlink:to="loc_ago_AnnuityReinsuranceSegmentMember_019eb852-df6b-77db-bdf7-c536187492af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssetManagementSegmentMember_019eb852-df6b-7039-94f8-6bbbec690215" xlink:href="ago-20260630.xsd#ago_AssetManagementSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-7827-b82f-a3f9938d54a8" xlink:to="loc_ago_AssetManagementSegmentMember_019eb852-df6b-7039-94f8-6bbbec690215" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7fbe-aa8a-e74dad2c3fcb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7f9c-81cf-4dcde7a1bc0a" xlink:to="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7fbe-aa8a-e74dad2c3fcb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7fbe-aa8a-e74dad2c3fcb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7fbe-aa8a-e74dad2c3fcb" xlink:to="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7fbe-aa8a-e74dad2c3fcb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7116-8d97-207c0a0984e3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7fbe-aa8a-e74dad2c3fcb" xlink:to="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7116-8d97-207c0a0984e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OperatingSegmentsExcludingIntersegmentEliminationMember_019eb852-df6b-76e2-bb0f-4751af9143d1" xlink:href="ago-20260630.xsd#ago_OperatingSegmentsExcludingIntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7116-8d97-207c0a0984e3" xlink:to="loc_ago_OperatingSegmentsExcludingIntersegmentEliminationMember_019eb852-df6b-76e2-bb0f-4751af9143d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019eb852-df6b-7877-a6cb-82feaa18b645" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7116-8d97-207c0a0984e3" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019eb852-df6b-7877-a6cb-82feaa18b645" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019eb852-df6b-737e-b6e9-29636e42a007" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7116-8d97-207c0a0984e3" xlink:to="loc_us-gaap_OperatingSegmentsMember_019eb852-df6b-737e-b6e9-29636e42a007" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019eb852-df6b-7b0d-8448-0adc3b224338" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_Revenues_019eb852-df6b-7b0d-8448-0adc3b224338" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019eb852-df6b-7e12-8dc1-788080e6fac5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderBenefitsAndClaimsIncurredNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019eb852-df6b-7e12-8dc1-788080e6fac5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense_019eb852-df6b-7c60-96fe-5ad0a52fa400" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense_019eb852-df6b-7c60-96fe-5ad0a52fa400" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019eb852-df6b-7430-86eb-be89ed488c5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeBenefitsAndShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019eb852-df6b-7430-86eb-be89ed488c5e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_019eb852-df6b-766d-b7d3-de2fce5d8a67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_019eb852-df6b-766d-b7d3-de2fce5d8a67" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_019eb852-df6b-7d28-b738-50c0f8e4ef88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_019eb852-df6b-7d28-b738-50c0f8e4ef88" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BenefitsLossesAndExpenses_019eb852-df6b-71dc-ab66-ba361a860466" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BenefitsLossesAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_BenefitsLossesAndExpenses_019eb852-df6b-71dc-ab66-ba361a860466" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019eb852-df6b-7e79-9b50-3228a1981754" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019eb852-df6b-7e79-9b50-3228a1981754" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019eb852-df6b-7c26-b0bc-4deca6a6c6ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019eb852-df6b-7c26-b0bc-4deca6a6c6ca" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019eb852-df6b-7aac-9e4d-86f075857ed9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_OperatingIncomeLoss_019eb852-df6b-7aac-9e4d-86f075857ed9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019eb852-df6b-7c5f-8cda-ce0f1f2ef7f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_us-gaap_NetInvestmentIncome_019eb852-df6b-7c5f-8cda-ce0f1f2ef7f0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_NoncashCompensationandOperatingExpensesSegment_019eb852-df6b-7f67-bf4d-40d696e422f0" xlink:href="ago-20260630.xsd#ago_NoncashCompensationandOperatingExpensesSegment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7a47-a7a0-bce0d7555a18" xlink:to="loc_ago_NoncashCompensationandOperatingExpensesSegment_019eb852-df6b-7f67-bf4d-40d696e422f0" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/SegmentInformationReconciliationofNetIncomeLossAttributabletoAGLtoSegmentAdjustedOperatingIncomeLossDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#SegmentInformationReconciliationofNetIncomeLossAttributabletoAGLtoSegmentAdjustedOperatingIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/SegmentInformationReconciliationofNetIncomeLossAttributabletoAGLtoSegmentAdjustedOperatingIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7960-ae91-a688e37134c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7960-ae91-a688e37134c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7856-96e6-feea7fc9fbdf" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7960-ae91-a688e37134c6" xlink:to="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7856-96e6-feea7fc9fbdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7856-96e6-feea7fc9fbdf_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7856-96e6-feea7fc9fbdf" xlink:to="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7856-96e6-feea7fc9fbdf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7063-ade1-6fc04c543442" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019eb852-df6b-7856-96e6-feea7fc9fbdf" xlink:to="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7063-ade1-6fc04c543442" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OperatingSegmentsAndCorporateNonSegmentMember_019eb852-df6b-7ef6-b1a9-f16523fd2095" xlink:href="ago-20260630.xsd#ago_OperatingSegmentsAndCorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7063-ade1-6fc04c543442" xlink:to="loc_ago_OperatingSegmentsAndCorporateNonSegmentMember_019eb852-df6b-7ef6-b1a9-f16523fd2095" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019eb852-df6b-730b-bbea-9ea769e35eff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_OperatingSegmentsAndCorporateNonSegmentMember_019eb852-df6b-7ef6-b1a9-f16523fd2095" xlink:to="loc_us-gaap_OperatingSegmentsMember_019eb852-df6b-730b-bbea-9ea769e35eff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019eb852-df6b-7994-93be-7f186a513d35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_OperatingSegmentsAndCorporateNonSegmentMember_019eb852-df6b-7ef6-b1a9-f16523fd2095" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019eb852-df6b-7994-93be-7f186a513d35" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019eb852-df6b-710c-bd2c-73ff87afb4fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7063-ade1-6fc04c543442" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019eb852-df6b-710c-bd2c-73ff87afb4fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_019eb852-df6b-75e3-b0c2-bde4315e095a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019eb852-df6b-7063-ade1-6fc04c543442" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_019eb852-df6b-75e3-b0c2-bde4315e095a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7a31-98ff-aa8309c79900" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7960-ae91-a688e37134c6" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7a31-98ff-aa8309c79900" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019eb852-df6b-7a31-98ff-aa8309c79900_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7a31-98ff-aa8309c79900" xlink:to="loc_us-gaap_SegmentDomain_019eb852-df6b-7a31-98ff-aa8309c79900_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019eb852-df6b-7386-906d-9ecdec95e6b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019eb852-df6b-7a31-98ff-aa8309c79900" xlink:to="loc_us-gaap_SegmentDomain_019eb852-df6b-7386-906d-9ecdec95e6b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantySegmentMember_019eb852-df6b-717c-9d9e-1d8ce003afe4" xlink:href="ago-20260630.xsd#ago_FinancialGuarantySegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-7386-906d-9ecdec95e6b3" xlink:to="loc_ago_FinancialGuarantySegmentMember_019eb852-df6b-717c-9d9e-1d8ce003afe4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AnnuityReinsuranceSegmentMember_019eb852-df6b-7f48-9e7e-7096025bad51" xlink:href="ago-20260630.xsd#ago_AnnuityReinsuranceSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-7386-906d-9ecdec95e6b3" xlink:to="loc_ago_AnnuityReinsuranceSegmentMember_019eb852-df6b-7f48-9e7e-7096025bad51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssetManagementSegmentMember_019eb852-df6b-7bbc-b9a3-6fa6df47d53d" xlink:href="ago-20260630.xsd#ago_AssetManagementSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019eb852-df6b-7386-906d-9ecdec95e6b3" xlink:to="loc_ago_AssetManagementSegmentMember_019eb852-df6b-7bbc-b9a3-6fa6df47d53d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ReconcilingItemsAxis_019eb852-df6b-7e3e-a0d3-9069673e9ad8" xlink:href="ago-20260630.xsd#ago_ReconcilingItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019eb852-df6b-7960-ae91-a688e37134c6" xlink:to="loc_ago_ReconcilingItemsAxis_019eb852-df6b-7e3e-a0d3-9069673e9ad8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7e3e-a0d3-9069673e9ad8_default" xlink:href="ago-20260630.xsd#ago_ReconcilingItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ago_ReconcilingItemsAxis_019eb852-df6b-7e3e-a0d3-9069673e9ad8" xlink:to="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7e3e-a0d3-9069673e9ad8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:href="ago-20260630.xsd#ago_ReconcilingItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ago_ReconcilingItemsAxis_019eb852-df6b-7e3e-a0d3-9069673e9ad8" xlink:to="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OperatingSegmentsAndCorporateNonSegmentMember_019eb852-df6b-7312-beaa-79644400adc6" xlink:href="ago-20260630.xsd#ago_OperatingSegmentsAndCorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_OperatingSegmentsAndCorporateNonSegmentMember_019eb852-df6b-7312-beaa-79644400adc6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_RealizedGainLossOnInvestmentsMember_019eb85e-0136-7164-892b-9eaa47055bd5" xlink:href="ago-20260630.xsd#ago_RealizedGainLossOnInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_RealizedGainLossOnInvestmentsMember_019eb85e-0136-7164-892b-9eaa47055bd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_NonCreditImpairmentRelatedUnrealizedFairValueGainsLossesOnCreditDerivativesMember_019eb852-df6b-7620-acc4-ff3fc038b895" xlink:href="ago-20260630.xsd#ago_NonCreditImpairmentRelatedUnrealizedFairValueGainsLossesOnCreditDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_NonCreditImpairmentRelatedUnrealizedFairValueGainsLossesOnCreditDerivativesMember_019eb852-df6b-7620-acc4-ff3fc038b895" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueGainsLossesOfDerivativesInAnnuityReinsuranceSegmentMember_019eb852-df6b-77f8-91b5-75e61c0e20df" xlink:href="ago-20260630.xsd#ago_FairValueGainsLossesOfDerivativesInAnnuityReinsuranceSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_FairValueGainsLossesOfDerivativesInAnnuityReinsuranceSegmentMember_019eb852-df6b-77f8-91b5-75e61c0e20df" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueGainsLossesOfEmbeddedDerivativesInFundsWithheldMember_019eb852-df6b-757f-9cb3-e9d09b3aec00" xlink:href="ago-20260630.xsd#ago_FairValueGainsLossesOfEmbeddedDerivativesInFundsWithheldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_FairValueGainsLossesOfEmbeddedDerivativesInFundsWithheldMember_019eb852-df6b-757f-9cb3-e9d09b3aec00" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueGainsLossesOnCommittedCapitalSecuritiesMember_019eb852-df6b-7d85-a0ba-f4ac16b27652" xlink:href="ago-20260630.xsd#ago_FairValueGainsLossesOnCommittedCapitalSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_FairValueGainsLossesOnCommittedCapitalSecuritiesMember_019eb852-df6b-7d85-a0ba-f4ac16b27652" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ForeignExchangeGainsLossesOnRemeasurmentOfPremiumsReceivableAndLossMember_019eb852-df6b-73ec-a7a3-ea3a79743c95" xlink:href="ago-20260630.xsd#ago_ForeignExchangeGainsLossesOnRemeasurmentOfPremiumsReceivableAndLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_ForeignExchangeGainsLossesOnRemeasurmentOfPremiumsReceivableAndLossMember_019eb852-df6b-73ec-a7a3-ea3a79743c95" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_IncomeTaxExpenseBenefitMember_019eb852-df6b-738f-94d7-bf2f97d881ac" xlink:href="ago-20260630.xsd#ago_IncomeTaxExpenseBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ReconcilingItemsDomain_019eb852-df6b-7692-b868-ca804bfecdad" xlink:to="loc_ago_IncomeTaxExpenseBenefitMember_019eb852-df6b-738f-94d7-bf2f97d881ac" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019eb852-df6b-7582-a24e-2619214831dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_Revenues_019eb852-df6b-7582-a24e-2619214831dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BenefitsLossesAndExpenses_019eb852-df6b-72e5-ad2a-e3098657eb0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BenefitsLossesAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_BenefitsLossesAndExpenses_019eb852-df6b-72e5-ad2a-e3098657eb0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019eb852-df6b-7107-8ea4-c2cf9f3b55bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019eb852-df6b-7107-8ea4-c2cf9f3b55bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019eb852-df6b-78ea-b19c-0a5b11a6a77d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019eb852-df6b-78ea-b19c-0a5b11a6a77d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019eb852-df6b-779b-af5d-f6a181eb5b04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019eb852-df6b-779b-af5d-f6a181eb5b04" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019eb852-df6b-7b4b-a5e1-709563446569" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019eb852-df6b-7590-8eab-da2614465581" xlink:to="loc_us-gaap_NetIncomeLoss_019eb852-df6b-7b4b-a5e1-709563446569" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/OutstandingExposureAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#OutstandingExposureAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/OutstandingExposureAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7156-8177-5105596f2bd2" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7156-8177-5105596f2bd2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb852-df6b-7061-8de9-b152849a03e1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7156-8177-5105596f2bd2" xlink:to="loc_srt_RangeAxis_019eb852-df6b-7061-8de9-b152849a03e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-df6b-7061-8de9-b152849a03e1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb852-df6b-7061-8de9-b152849a03e1" xlink:to="loc_srt_RangeMember_019eb852-df6b-7061-8de9-b152849a03e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-df6b-7268-a8d0-0834261a71aa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb852-df6b-7061-8de9-b152849a03e1" xlink:to="loc_srt_RangeMember_019eb852-df6b-7268-a8d0-0834261a71aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb852-df6b-750d-a405-358b94242a81" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-df6b-7268-a8d0-0834261a71aa" xlink:to="loc_srt_MinimumMember_019eb852-df6b-750d-a405-358b94242a81" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_019eb852-df6b-7fb4-bee0-8eb7a98ab557" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7156-8177-5105596f2bd2" xlink:to="loc_us-gaap_OtherCommitmentsAxis_019eb852-df6b-7fb4-bee0-8eb7a98ab557" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_019eb852-df6b-7fb4-bee0-8eb7a98ab557_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_019eb852-df6b-7fb4-bee0-8eb7a98ab557" xlink:to="loc_us-gaap_OtherCommitmentsDomain_019eb852-df6b-7fb4-bee0-8eb7a98ab557_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_019eb852-df6b-7ec1-ba4f-648b11ab31cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_019eb852-df6b-7fb4-bee0-8eb7a98ab557" xlink:to="loc_us-gaap_OtherCommitmentsDomain_019eb852-df6b-7ec1-ba4f-648b11ab31cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CommitmenttoProvideGuaranteesMember_019eb852-df6b-79a5-9b4b-ffc670b707e1" xlink:href="ago-20260630.xsd#ago_CommitmenttoProvideGuaranteesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_019eb852-df6b-7ec1-ba4f-648b11ab31cf" xlink:to="loc_ago_CommitmenttoProvideGuaranteesMember_019eb852-df6b-79a5-9b4b-ffc670b707e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-723f-a5b7-8f856eeb2f17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7156-8177-5105596f2bd2" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-723f-a5b7-8f856eeb2f17" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-723f-a5b7-8f856eeb2f17_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-723f-a5b7-8f856eeb2f17" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-723f-a5b7-8f856eeb2f17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7335-8637-9037a3f13f69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-723f-a5b7-8f856eeb2f17" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7335-8637-9037a3f13f69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sic_Z3721_019eb852-df6b-75bf-81e0-b374683d8980" xlink:href="https://xbrl.sec.gov/sic/2026/sic-2026.xsd#sic_Z3721"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7335-8637-9037a3f13f69" xlink:to="loc_sic_Z3721_019eb852-df6b-75bf-81e0-b374683d8980" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-df6b-7a9f-9a8d-a39ae6ae6ced" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7335-8637-9037a3f13f69" xlink:to="loc_ago_PublicFinanceMember_019eb852-df6b-7a9f-9a8d-a39ae6ae6ced" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-796f-8ffa-ef89847c29b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7335-8637-9037a3f13f69" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-796f-8ffa-ef89847c29b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7a9c-8f13-b0847bef3800" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7156-8177-5105596f2bd2" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7a9c-8f13-b0847bef3800" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7a9c-8f13-b0847bef3800_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7a9c-8f13-b0847bef3800" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7a9c-8f13-b0847bef3800_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-717f-a9c3-818cbd4eaed0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7a9c-8f13-b0847bef3800" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-717f-a9c3-818cbd4eaed0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-78a3-9ac1-244110773b39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-717f-a9c3-818cbd4eaed0" xlink:to="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-78a3-9ac1-244110773b39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_NumberOfSurveillanceCategories_019eb852-df6b-718d-9dc9-f2790513aaea" xlink:href="ago-20260630.xsd#ago_NumberOfSurveillanceCategories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_ago_NumberOfSurveillanceCategories_019eb852-df6b-718d-9dc9-f2790513aaea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsAggregateProbabilityWeightOfPossibleLossesPercentage_019eb852-df6b-7e88-b44a-a224bebbc157" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsAggregateProbabilityWeightOfPossibleLossesPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_ago_InsuredFinancialObligationsAggregateProbabilityWeightOfPossibleLossesPercentage_019eb852-df6b-7e88-b44a-a224bebbc157" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsLossMitigationSecurities_019eb852-df6b-729d-85fb-4dde1518b475" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsLossMitigationSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_ago_InsuredFinancialObligationsLossMitigationSecurities_019eb852-df6b-729d-85fb-4dde1518b475" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SpecialtyBusinessGrossPar_019eb852-df6b-757c-a078-4320f28e9e84" xlink:href="ago-20260630.xsd#ago_SpecialtyBusinessGrossPar"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_ago_SpecialtyBusinessGrossPar_019eb852-df6b-757c-a078-4320f28e9e84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SpecialtyBusinessNetPar_019eb852-df6b-7708-90da-7466c877a13c" xlink:href="ago-20260630.xsd#ago_SpecialtyBusinessNetPar"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_ago_SpecialtyBusinessNetPar_019eb852-df6b-7708-90da-7466c877a13c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_019eb852-df6b-7b96-8d04-f75e79d80025" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7e25-a250-ff4edda7682a" xlink:to="loc_us-gaap_OtherCommitment_019eb852-df6b-7b96-8d04-f75e79d80025" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/OutstandingExposureDebtServiceOutstandingDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#OutstandingExposureDebtServiceOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/OutstandingExposureDebtServiceOutstandingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7996-90c3-34c00837a35d" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7001-89e2-06582d465bfb" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7996-90c3-34c00837a35d" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7001-89e2-06582d465bfb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7562-b766-231160917635" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7001-89e2-06582d465bfb" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7562-b766-231160917635" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7562-b766-231160917635_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7562-b766-231160917635" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7562-b766-231160917635_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-76ae-9b22-ae59b838e11a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7562-b766-231160917635" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-76ae-9b22-ae59b838e11a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-df6b-7d71-b857-0037ae7019fb" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-76ae-9b22-ae59b838e11a" xlink:to="loc_ago_PublicFinanceMember_019eb852-df6b-7d71-b857-0037ae7019fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-736e-bfb9-1d3aff8372e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-76ae-9b22-ae59b838e11a" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-736e-bfb9-1d3aff8372e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DebtServiceAbstract_019eb852-df6b-750b-a7c7-fbdb09ee222f" xlink:href="ago-20260630.xsd#ago_DebtServiceAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7996-90c3-34c00837a35d" xlink:to="loc_ago_DebtServiceAbstract_019eb852-df6b-750b-a7c7-fbdb09ee222f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingGross_019eb852-df6b-7da3-8666-041cad4829c4" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DebtServiceAbstract_019eb852-df6b-750b-a7c7-fbdb09ee222f" xlink:to="loc_ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingGross_019eb852-df6b-7da3-8666-041cad4829c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingNet_019eb852-df6b-74a8-86d8-a4dc9ee8d15e" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DebtServiceAbstract_019eb852-df6b-750b-a7c7-fbdb09ee222f" xlink:to="loc_ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingNet_019eb852-df6b-74a8-86d8-a4dc9ee8d15e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ParOutstandingAbstract_019eb852-df6b-7690-a715-094e891bb519" xlink:href="ago-20260630.xsd#ago_ParOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7996-90c3-34c00837a35d" xlink:to="loc_ago_ParOutstandingAbstract_019eb852-df6b-7690-a715-094e891bb519" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountGross_019eb852-df6b-7d80-bbb0-6ccdfed7b3fa" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipalAmountGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ParOutstandingAbstract_019eb852-df6b-7690-a715-094e891bb519" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountGross_019eb852-df6b-7d80-bbb0-6ccdfed7b3fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-7646-9aaf-e107ed2c3d1f" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ParOutstandingAbstract_019eb852-df6b-7690-a715-094e891bb519" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-7646-9aaf-e107ed2c3d1f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/OutstandingExposureFinancialGuarantyPortfoliobyInternalRatingDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#OutstandingExposureFinancialGuarantyPortfoliobyInternalRatingDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/OutstandingExposureFinancialGuarantyPortfoliobyInternalRatingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7747-971a-ccde81a9af20" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-77f0-ab4d-04bcce9eccaa" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7747-971a-ccde81a9af20" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-77f0-ab4d-04bcce9eccaa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7dfc-a17d-522e1debf38c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-77f0-ab4d-04bcce9eccaa" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7dfc-a17d-522e1debf38c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7dfc-a17d-522e1debf38c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7dfc-a17d-522e1debf38c" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7dfc-a17d-522e1debf38c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7570-913d-957eae1e77f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7dfc-a17d-522e1debf38c" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7570-913d-957eae1e77f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-df6b-7444-8b15-ade8bb13de0a" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7570-913d-957eae1e77f1" xlink:to="loc_ago_PublicFinanceMember_019eb852-df6b-7444-8b15-ade8bb13de0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-7ecd-b6d7-ab5b79f38cdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7570-913d-957eae1e77f1" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-7ecd-b6d7-ab5b79f38cdc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7779-b6ec-9c4f1e193347" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-77f0-ab4d-04bcce9eccaa" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7779-b6ec-9c4f1e193347" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7779-b6ec-9c4f1e193347_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7779-b6ec-9c4f1e193347" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7779-b6ec-9c4f1e193347_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-7779-b6ec-9c4f1e193347" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalInvestmentGradeAAAMember_019eb852-df6b-71aa-859f-5a10b625806f" xlink:href="ago-20260630.xsd#ago_InternalInvestmentGradeAAAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:to="loc_ago_InternalInvestmentGradeAAAMember_019eb852-df6b-71aa-859f-5a10b625806f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalInvestmentGradeAAMember_019eb852-df6b-7b01-87bf-83ad85af3863" xlink:href="ago-20260630.xsd#ago_InternalInvestmentGradeAAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:to="loc_ago_InternalInvestmentGradeAAMember_019eb852-df6b-7b01-87bf-83ad85af3863" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalInvestmentGradeAMember_019eb852-df6b-798f-b77c-d5e02a90bfc1" xlink:href="ago-20260630.xsd#ago_InternalInvestmentGradeAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:to="loc_ago_InternalInvestmentGradeAMember_019eb852-df6b-798f-b77c-d5e02a90bfc1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalInvestmentGradeBBBMember_019eb852-df6b-7b90-be79-81b52ad80444" xlink:href="ago-20260630.xsd#ago_InternalInvestmentGradeBBBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:to="loc_ago_InternalInvestmentGradeBBBMember_019eb852-df6b-7b90-be79-81b52ad80444" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-7a45-b4c2-97943b8f654d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7c1e-aee0-753310172154" xlink:to="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-7a45-b4c2-97943b8f654d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-df6b-7f91-8ac1-536404fa39f5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-77f0-ab4d-04bcce9eccaa" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-df6b-7f91-8ac1-536404fa39f5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7f91-8ac1-536404fa39f5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-df6b-7f91-8ac1-536404fa39f5" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7f91-8ac1-536404fa39f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7a08-b614-de90517e4aab" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-df6b-7f91-8ac1-536404fa39f5" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7a08-b614-de90517e4aab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-df6b-78c0-b474-bf13b8813a71" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7a08-b614-de90517e4aab" xlink:to="loc_country_US_019eb852-df6b-78c0-b474-bf13b8813a71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019eb852-df6b-7ada-9179-fdc8c448bea6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7a08-b614-de90517e4aab" xlink:to="loc_us-gaap_NonUsMember_019eb852-df6b-7ada-9179-fdc8c448bea6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-7522-8011-72c9c248d0f7" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7747-971a-ccde81a9af20" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-7522-8011-72c9c248d0f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipleAmountPercentage_019eb852-df6b-76e4-8e91-2778a8a784f3" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipleAmountPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7747-971a-ccde81a9af20" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipleAmountPercentage_019eb852-df6b-76e4-8e91-2778a8a784f3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/OutstandingExposureComponentsofBIGNetParOutstandingDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#OutstandingExposureComponentsofBIGNetParOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/OutstandingExposureComponentsofBIGNetParOutstandingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-77b9-aad2-4399204afc4c" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7ce3-a6c6-e78d7f70fed2" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-77b9-aad2-4399204afc4c" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7ce3-a6c6-e78d7f70fed2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-df6b-7272-87c4-476689737d62" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7ce3-a6c6-e78d7f70fed2" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-df6b-7272-87c4-476689737d62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7272-87c4-476689737d62_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-df6b-7272-87c4-476689737d62" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7272-87c4-476689737d62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7138-a3b3-d8ed4f9f8d49" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-df6b-7272-87c4-476689737d62" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7138-a3b3-d8ed4f9f8d49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-df6b-71b6-a17f-c8859773c14d" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7138-a3b3-d8ed4f9f8d49" xlink:to="loc_country_US_019eb852-df6b-71b6-a17f-c8859773c14d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019eb852-df6b-713e-b13c-cabb395ad036" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-df6b-7138-a3b3-d8ed4f9f8d49" xlink:to="loc_us-gaap_NonUsMember_019eb852-df6b-713e-b13c-cabb395ad036" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-73d0-a895-220f3ab4f914" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7ce3-a6c6-e78d7f70fed2" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-73d0-a895-220f3ab4f914" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-73d0-a895-220f3ab4f914_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-73d0-a895-220f3ab4f914" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-73d0-a895-220f3ab4f914_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7220-9f88-ff254e9b911f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-73d0-a895-220f3ab4f914" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7220-9f88-ff254e9b911f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-788b-be84-b80be20151be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-7220-9f88-ff254e9b911f" xlink:to="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-788b-be84-b80be20151be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7e29-b1e6-aea804ba8cf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7ce3-a6c6-e78d7f70fed2" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7e29-b1e6-aea804ba8cf0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7e29-b1e6-aea804ba8cf0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SurveillanceCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7e29-b1e6-aea804ba8cf0" xlink:to="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7e29-b1e6-aea804ba8cf0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7289-9324-adb041d31b0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SurveillanceCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7e29-b1e6-aea804ba8cf0" xlink:to="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7289-9324-adb041d31b0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel1Member_019eb852-df6b-7c8c-83cf-d064edfa6af7" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7289-9324-adb041d31b0f" xlink:to="loc_ago_InternalNoninvestmentGradeLevel1Member_019eb852-df6b-7c8c-83cf-d064edfa6af7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel2Member_019eb852-df6b-71c5-8527-174c58c56125" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7289-9324-adb041d31b0f" xlink:to="loc_ago_InternalNoninvestmentGradeLevel2Member_019eb852-df6b-71c5-8527-174c58c56125" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel3Member_019eb852-df6b-7b1e-9ba0-95ca5a2e7539" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7289-9324-adb041d31b0f" xlink:to="loc_ago_InternalNoninvestmentGradeLevel3Member_019eb852-df6b-7b1e-9ba0-95ca5a2e7539" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_TotalNoninvestmentGradeMember_019eb852-df6b-78e0-b207-a2ba8cee2eed" xlink:href="ago-20260630.xsd#ago_TotalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7289-9324-adb041d31b0f" xlink:to="loc_ago_TotalNoninvestmentGradeMember_019eb852-df6b-78e0-b207-a2ba8cee2eed" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-751b-928f-2f4a88c3edaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7ce3-a6c6-e78d7f70fed2" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-751b-928f-2f4a88c3edaa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-751b-928f-2f4a88c3edaa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-751b-928f-2f4a88c3edaa" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-751b-928f-2f4a88c3edaa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-78e7-8aab-e51e1e794a44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-751b-928f-2f4a88c3edaa" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-78e7-8aab-e51e1e794a44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-df6b-77ee-8134-8bb626884a24" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-78e7-8aab-e51e1e794a44" xlink:to="loc_ago_PublicFinanceMember_019eb852-df6b-77ee-8134-8bb626884a24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-df6b-7d07-81b1-d3d1afbfc840" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-78e7-8aab-e51e1e794a44" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-df6b-7d07-81b1-d3d1afbfc840" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherStructuredFinanceMember_019eb852-df6b-7cda-8b3a-5256b59f20f5" xlink:href="ago-20260630.xsd#ago_OtherStructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-78e7-8aab-e51e1e794a44" xlink:to="loc_ago_OtherStructuredFinanceMember_019eb852-df6b-7cda-8b3a-5256b59f20f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-7208-9d4e-a3ee94fceaf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-78e7-8aab-e51e1e794a44" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-df6b-7208-9d4e-a3ee94fceaf5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-7fbf-9767-2d2a8f0871ca" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-77b9-aad2-4399204afc4c" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-7fbf-9767-2d2a8f0871ca" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/OutstandingExposureBIGNetParOutstandingDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#OutstandingExposureBIGNetParOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/OutstandingExposureBIGNetParOutstandingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7353-a0d0-66b2c82634dc" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7353-a0d0-66b2c82634dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-741f-a7e5-cd29c89e2ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7353-a0d0-66b2c82634dc" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-741f-a7e5-cd29c89e2ec9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-741f-a7e5-cd29c89e2ec9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-741f-a7e5-cd29c89e2ec9" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-741f-a7e5-cd29c89e2ec9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-78c4-b0ec-65a0ac64dd34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-df6b-741f-a7e5-cd29c89e2ec9" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-78c4-b0ec-65a0ac64dd34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-7569-b59f-9431e2639583" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-df6b-78c4-b0ec-65a0ac64dd34" xlink:to="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-df6b-7569-b59f-9431e2639583" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7f2c-833a-e95f81a371ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7353-a0d0-66b2c82634dc" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7f2c-833a-e95f81a371ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7f2c-833a-e95f81a371ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SurveillanceCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7f2c-833a-e95f81a371ad" xlink:to="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7f2c-833a-e95f81a371ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7c8b-bfa8-ec6cb4228171" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SurveillanceCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-df6b-7f2c-833a-e95f81a371ad" xlink:to="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7c8b-bfa8-ec6cb4228171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel1Member_019eb852-df6b-7fd3-8f8f-77c191ad46cc" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7c8b-bfa8-ec6cb4228171" xlink:to="loc_ago_InternalNoninvestmentGradeLevel1Member_019eb852-df6b-7fd3-8f8f-77c191ad46cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel2Member_019eb852-df6b-723b-991a-fe737999c15c" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7c8b-bfa8-ec6cb4228171" xlink:to="loc_ago_InternalNoninvestmentGradeLevel2Member_019eb852-df6b-723b-991a-fe737999c15c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel3Member_019eb852-df6b-7b08-82be-e3ae61d2fa65" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-df6b-7c8b-bfa8-ec6cb4228171" xlink:to="loc_ago_InternalNoninvestmentGradeLevel3Member_019eb852-df6b-7b08-82be-e3ae61d2fa65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalNet_019eb852-df6b-78c4-b3a9-b4151792f051" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalNet_019eb852-df6b-78c4-b3a9-b4151792f051" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyContractsAccountedforasCreditDerivativesOutstandingPrincipalAmount_019eb852-df6b-74e4-97f1-89e13e5b0bbc" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyContractsAccountedforasCreditDerivativesOutstandingPrincipalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_ago_FinancialGuarantyContractsAccountedforasCreditDerivativesOutstandingPrincipalAmount_019eb852-df6b-74e4-97f1-89e13e5b0bbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-775d-8f0b-90c7c7d43769" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-df6b-775d-8f0b-90c7c7d43769" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfContractsIssuedAndOutstanding_019eb852-df6b-7c11-8394-44f6651f25c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfContractsIssuedAndOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfContractsIssuedAndOutstanding_019eb852-df6b-7c11-8394-44f6651f25c8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesNumberOfContracts_019eb852-df6b-7b96-a214-bd69fa64ac32" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesNumberOfContracts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesNumberOfContracts_019eb852-df6b-7b96-a214-bd69fa64ac32" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsNumberofContracts_019eb852-df6b-756b-837a-aca1afcf6ee4" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsNumberofContracts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-756e-a80c-4fb30c20206b" xlink:to="loc_ago_InsuredFinancialObligationsNumberofContracts_019eb852-df6b-756b-837a-aca1afcf6ee4" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/OutstandingExposureScheduleofNonFinancialGuarantyExposureDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#OutstandingExposureScheduleofNonFinancialGuarantyExposureDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/OutstandingExposureScheduleofNonFinancialGuarantyExposureDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7f3c-a330-7cce87dc4f1f" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7c07-a680-a17bb8b5c2d1" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7f3c-a330-7cce87dc4f1f" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7c07-a680-a17bb8b5c2d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7305-bf05-3f858371263a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsTable_019eb852-df6b-7c07-a680-a17bb8b5c2d1" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7305-bf05-3f858371263a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7305-bf05-3f858371263a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7305-bf05-3f858371263a" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7305-bf05-3f858371263a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7778-ad03-ca52bd5b8d2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-df6b-7305-bf05-3f858371263a" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7778-ad03-ca52bd5b8d2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DiversifiedRealEstateMember_019eb852-df6b-71c6-8fde-7d754b243772" xlink:href="ago-20260630.xsd#ago_DiversifiedRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7778-ad03-ca52bd5b8d2a" xlink:to="loc_ago_DiversifiedRealEstateMember_019eb852-df6b-71c6-8fde-7d754b243772" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuranceReserveFinancingAndSecuritizationsMember_019eb852-df6b-7bef-94b1-488d99ff9f23" xlink:href="ago-20260630.xsd#ago_InsuranceReserveFinancingAndSecuritizationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7778-ad03-ca52bd5b8d2a" xlink:to="loc_ago_InsuranceReserveFinancingAndSecuritizationsMember_019eb852-df6b-7bef-94b1-488d99ff9f23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PooledCorporateObligationMember_019eb852-df6b-7804-960b-a38e03d099e4" xlink:href="ago-20260630.xsd#ago_PooledCorporateObligationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7778-ad03-ca52bd5b8d2a" xlink:to="loc_ago_PooledCorporateObligationMember_019eb852-df6b-7804-960b-a38e03d099e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sic_Z3721_019eb852-df6b-7753-aee7-ff10542def3f" xlink:href="https://xbrl.sec.gov/sic/2026/sic-2026.xsd#sic_Z3721"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-df6b-7778-ad03-ca52bd5b8d2a" xlink:to="loc_sic_Z3721_019eb852-df6b-7753-aee7-ff10542def3f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SpecialtyBusinessGrossPar_019eb852-df6b-7ca8-8fb7-e060fa001cdf" xlink:href="ago-20260630.xsd#ago_SpecialtyBusinessGrossPar"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7f3c-a330-7cce87dc4f1f" xlink:to="loc_ago_SpecialtyBusinessGrossPar_019eb852-df6b-7ca8-8fb7-e060fa001cdf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SpecialtyBusinessNetPar_019eb852-df6b-7a64-ad9d-8f73398be726" xlink:href="ago-20260630.xsd#ago_SpecialtyBusinessNetPar"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofInsuredFinancialObligationsLineItems_019eb852-df6b-7f3c-a330-7cce87dc4f1f" xlink:to="loc_ago_SpecialtyBusinessNetPar_019eb852-df6b-7a64-ad9d-8f73398be726" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ExpectedLosstobePaidRecoveredAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e02f-7907-8b58-6547e2f38050" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e02f-7907-8b58-6547e2f38050" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7907-8b58-6547e2f38050_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e02f-7907-8b58-6547e2f38050" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7907-8b58-6547e2f38050_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e02f-71ae-9551-236f35cfc50e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e02f-7907-8b58-6547e2f38050" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e02f-71ae-9551-236f35cfc50e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e02f-72ff-913c-7e14774e4dbc" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e02f-71ae-9551-236f35cfc50e" xlink:to="loc_country_US_019eb852-e02f-72ff-913c-7e14774e4dbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_PR_019eb852-e02f-7680-b960-9dd3b633cab3" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_PR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e02f-71ae-9551-236f35cfc50e" xlink:to="loc_country_PR_019eb852-e02f-7680-b960-9dd3b633cab3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7a49-8ed8-02e7ab878920" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7a49-8ed8-02e7ab878920" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-7a49-8ed8-02e7ab878920_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7a49-8ed8-02e7ab878920" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-7a49-8ed8-02e7ab878920_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7a49-8ed8-02e7ab878920" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e02f-7c0f-a33d-cd2a8c771ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e02f-7c0f-a33d-cd2a8c771ff3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HomeEquityMember_019eb852-e02f-713a-b314-fed12696ff1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HomeEquityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_us-gaap_HomeEquityMember_019eb852-e02f-713a-b314-fed12696ff1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_EuropeanRenewableEnergyMember_019eb852-e02f-7c45-9334-9035075bc953" xlink:href="ago-20260630.xsd#ago_EuropeanRenewableEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_ago_EuropeanRenewableEnergyMember_019eb852-e02f-7c45-9334-9035075bc953" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ThamesWaterUtilitiesFinancePLCMember_019eb852-e02f-71d9-af71-9336ade58f71" xlink:href="ago-20260630.xsd#ago_ThamesWaterUtilitiesFinancePLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_ago_ThamesWaterUtilitiesFinancePLCMember_019eb852-e02f-71d9-af71-9336ade58f71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_U.K.StudentAccommodationsMember_019eb852-e02f-7154-9d5e-c53785b0b9c4" xlink:href="ago-20260630.xsd#ago_U.K.StudentAccommodationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_ago_U.K.StudentAccommodationsMember_019eb852-e02f-7154-9d5e-c53785b0b9c4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_U.K.NationalHealthServiceTrustsMember_019eb852-e02f-795c-ab71-8108c6f481de" xlink:href="ago-20260630.xsd#ago_U.K.NationalHealthServiceTrustsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_ago_U.K.NationalHealthServiceTrustsMember_019eb852-e02f-795c-ab71-8108c6f481de" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_U.S.TransportationMember_019eb852-e02f-7118-a458-0c31f2b202f6" xlink:href="ago-20260630.xsd#ago_U.S.TransportationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-798e-9a79-238916bcbdf7" xlink:to="loc_ago_U.S.TransportationMember_019eb852-e02f-7118-a458-0c31f2b202f6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7e24-b17b-3e501c683722" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7e24-b17b-3e501c683722" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-7e24-b17b-3e501c683722_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7e24-b17b-3e501c683722" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-7e24-b17b-3e501c683722_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-77f5-ba65-24f15c183a58" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7e24-b17b-3e501c683722" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-77f5-ba65-24f15c183a58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FirstMortgageMember_019eb852-e02f-7c1b-af1c-603b421b2d6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FirstMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-77f5-ba65-24f15c183a58" xlink:to="loc_us-gaap_FirstMortgageMember_019eb852-e02f-7c1b-af1c-603b421b2d6b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecondMortgageMember_019eb852-e02f-7ff6-83b9-75effe4926e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecondMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-77f5-ba65-24f15c183a58" xlink:to="loc_us-gaap_SecondMortgageMember_019eb852-e02f-7ff6-83b9-75effe4926e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019eb852-e02f-79b8-a5f3-fabbc6ca2d26" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_srt_StatementScenarioAxis_019eb852-e02f-79b8-a5f3-fabbc6ca2d26" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019eb852-e02f-79b8-a5f3-fabbc6ca2d26_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019eb852-e02f-79b8-a5f3-fabbc6ca2d26" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019eb852-e02f-79b8-a5f3-fabbc6ca2d26_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019eb852-e02f-733b-b10b-aa38735e64ee" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019eb852-e02f-79b8-a5f3-fabbc6ca2d26" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019eb852-e02f-733b-b10b-aa38735e64ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MoreStressfulEnvironmentMember_019eb852-e02f-7b87-9719-448a57fdeda7" xlink:href="ago-20260630.xsd#ago_MoreStressfulEnvironmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019eb852-e02f-733b-b10b-aa38735e64ee" xlink:to="loc_ago_MoreStressfulEnvironmentMember_019eb852-e02f-7b87-9719-448a57fdeda7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LeastStressfulEnvironmentMember_019eb852-e02f-771a-b8e8-6fcb23cc557a" xlink:href="ago-20260630.xsd#ago_LeastStressfulEnvironmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019eb852-e02f-733b-b10b-aa38735e64ee" xlink:to="loc_ago_LeastStressfulEnvironmentMember_019eb852-e02f-771a-b8e8-6fcb23cc557a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e02f-7800-86db-dc2290b29012" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e02f-7800-86db-dc2290b29012" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e02f-7800-86db-dc2290b29012_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e02f-7800-86db-dc2290b29012" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e02f-7800-86db-dc2290b29012_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e02f-7dc5-b2dc-4e674339a21d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e02f-7800-86db-dc2290b29012" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e02f-7dc5-b2dc-4e674339a21d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HomeEquityMember_019eb852-e02f-7f9f-9353-85a940520f10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HomeEquityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e02f-7dc5-b2dc-4e674339a21d" xlink:to="loc_us-gaap_HomeEquityMember_019eb852-e02f-7f9f-9353-85a940520f10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanTypeAxis_019eb852-e02f-728a-8dc5-3f41ea7ea428" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanTypeAxis_019eb852-e02f-728a-8dc5-3f41ea7ea428" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanTypeDomain_019eb852-e02f-728a-8dc5-3f41ea7ea428_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanTypeAxis_019eb852-e02f-728a-8dc5-3f41ea7ea428" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanTypeDomain_019eb852-e02f-728a-8dc5-3f41ea7ea428_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanTypeDomain_019eb852-e02f-7e48-8268-0aff71894494" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanTypeAxis_019eb852-e02f-728a-8dc5-3f41ea7ea428" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanTypeDomain_019eb852-e02f-7e48-8268-0aff71894494" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecondMortgageMember_019eb852-e02f-70e1-84ee-84a5d4bb37b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecondMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanTypeDomain_019eb852-e02f-7e48-8268-0aff71894494" xlink:to="loc_us-gaap_SecondMortgageMember_019eb852-e02f-70e1-84ee-84a5d4bb37b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7a30-b08a-e57e70929ffe" xlink:href="ago-20260630.xsd#ago_DeferredLoanRecoveryScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7a30-b08a-e57e70929ffe" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7a30-b08a-e57e70929ffe_default" xlink:href="ago-20260630.xsd#ago_DeferredLoanRecoveryScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7a30-b08a-e57e70929ffe" xlink:to="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7a30-b08a-e57e70929ffe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7a4d-b612-61e64246a4d2" xlink:href="ago-20260630.xsd#ago_DeferredLoanRecoveryScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7a30-b08a-e57e70929ffe" xlink:to="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7a4d-b612-61e64246a4d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MoreStressfulEnvironmentMember_019eb852-e02f-797f-8868-73fa36ff29c8" xlink:href="ago-20260630.xsd#ago_MoreStressfulEnvironmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7a4d-b612-61e64246a4d2" xlink:to="loc_ago_MoreStressfulEnvironmentMember_019eb852-e02f-797f-8868-73fa36ff29c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LeastStressfulEnvironmentMember_019eb852-e02f-7339-8123-5d3a81d4ef93" xlink:href="ago-20260630.xsd#ago_LeastStressfulEnvironmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7a4d-b612-61e64246a4d2" xlink:to="loc_ago_LeastStressfulEnvironmentMember_019eb852-e02f-7339-8123-5d3a81d4ef93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesAxis_019eb852-e02f-735f-a83d-56f11430bf63" xlink:href="ago-20260630.xsd#ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesAxis_019eb852-e02f-735f-a83d-56f11430bf63" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain_019eb852-e02f-735f-a83d-56f11430bf63_default" xlink:href="ago-20260630.xsd#ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesAxis_019eb852-e02f-735f-a83d-56f11430bf63" xlink:to="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain_019eb852-e02f-735f-a83d-56f11430bf63_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain_019eb852-e02f-73da-8098-2be030e18964" xlink:href="ago-20260630.xsd#ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesAxis_019eb852-e02f-735f-a83d-56f11430bf63" xlink:to="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain_019eb852-e02f-73da-8098-2be030e18964" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_NonDefaultingPuertoRicoExposuresMember_019eb852-e02f-768b-9114-33a5723957f0" xlink:href="ago-20260630.xsd#ago_NonDefaultingPuertoRicoExposuresMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain_019eb852-e02f-73da-8098-2be030e18964" xlink:to="loc_ago_NonDefaultingPuertoRicoExposuresMember_019eb852-e02f-768b-9114-33a5723957f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PuertoRicoDefaultedExposuresSubjectToAPlanSupportAgreementMember_019eb852-e02f-7f3a-8108-2d253bae3cd2" xlink:href="ago-20260630.xsd#ago_PuertoRicoDefaultedExposuresSubjectToAPlanSupportAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_LoansInsuredOrGuaranteeForGovernmentAuthoritiesDomain_019eb852-e02f-73da-8098-2be030e18964" xlink:to="loc_ago_PuertoRicoDefaultedExposuresSubjectToAPlanSupportAgreementMember_019eb852-e02f-7f3a-8108-2d253bae3cd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019eb852-e02f-70a2-b6f3-8837ae7808c6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_srt_CounterpartyNameAxis_019eb852-e02f-70a2-b6f3-8837ae7808c6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019eb852-e02f-70a2-b6f3-8837ae7808c6_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019eb852-e02f-70a2-b6f3-8837ae7808c6" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019eb852-e02f-70a2-b6f3-8837ae7808c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019eb852-e02f-743f-b7d3-ea93cd101f4b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019eb852-e02f-70a2-b6f3-8837ae7808c6" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019eb852-e02f-743f-b7d3-ea93cd101f4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PuertoRicoElectricPowerAuthorityMember_019eb852-e02f-7521-90f9-0fac8ec321d4" xlink:href="ago-20260630.xsd#ago_PuertoRicoElectricPowerAuthorityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019eb852-e02f-743f-b7d3-ea93cd101f4b" xlink:to="loc_ago_PuertoRicoElectricPowerAuthorityMember_019eb852-e02f-7521-90f9-0fac8ec321d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e02f-730b-908c-56d1a14c563d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-758c-aaa1-5c64afeb2abf" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e02f-730b-908c-56d1a14c563d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e02f-730b-908c-56d1a14c563d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e02f-730b-908c-56d1a14c563d" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e02f-730b-908c-56d1a14c563d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e02f-7bce-8db6-29c7f61d4eed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e02f-730b-908c-56d1a14c563d" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e02f-7bce-8db6-29c7f61d4eed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-e02f-75d4-9fb0-e65e5f97cefe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e02f-7bce-8db6-29c7f61d4eed" xlink:to="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-e02f-75d4-9fb0-e65e5f97cefe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsInsuredCreditPerformanceofGuaranteedObligationsTerm_019eb852-e02f-7a17-b555-645e0757b2e0" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsInsuredCreditPerformanceofGuaranteedObligationsTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_InsuredFinancialObligationsInsuredCreditPerformanceofGuaranteedObligationsTerm_019eb852-e02f-7a17-b555-645e0757b2e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsLiabilityforUnpaidClaimsAdjustmentExpenseClaimsPaid_019eb852-e02f-7960-af7e-5b9d6ff5398e" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsLiabilityforUnpaidClaimsAdjustmentExpenseClaimsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_InsuredFinancialObligationsLiabilityforUnpaidClaimsAdjustmentExpenseClaimsPaid_019eb852-e02f-7960-af7e-5b9d6ff5398e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ExpectedLossAdjustmentExpenseToBePaid_019eb852-e02f-7454-acc1-8fafd344246f" xlink:href="ago-20260630.xsd#ago_ExpectedLossAdjustmentExpenseToBePaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_ExpectedLossAdjustmentExpenseToBePaid_019eb852-e02f-7454-acc1-8fafd344246f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceEstimatedFutureRecoveriesOfClaimsPaid_019eb852-e02f-70e7-8929-d03dfbfe4199" xlink:href="ago-20260630.xsd#ago_PublicFinanceEstimatedFutureRecoveriesOfClaimsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_PublicFinanceEstimatedFutureRecoveriesOfClaimsPaid_019eb852-e02f-70e7-8929-d03dfbfe4199" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-e02f-78dd-9998-c6ac5417b9a4" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet_019eb852-e02f-78dd-9998-c6ac5417b9a4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingNet_019eb852-e02f-75c9-9903-c279f3aa4ba8" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_InsuredFinancialObligationsInsuredContractualPaymentsOutstandingNet_019eb852-e02f-75c9-9903-c279f3aa4ba8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LossContingencyPlaintiffTerminatedBoardMembers_019eb852-e02f-72e5-a616-3885d915dd54" xlink:href="ago-20260630.xsd#ago_LossContingencyPlaintiffTerminatedBoardMembers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_LossContingencyPlaintiffTerminatedBoardMembers_019eb852-e02f-72e5-a616-3885d915dd54" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LossContingencyPlaintiffTotalBoardMembers_019eb852-e02f-7f23-9c6b-6e47810837e4" xlink:href="ago-20260630.xsd#ago_LossContingencyPlaintiffTotalBoardMembers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_LossContingencyPlaintiffTotalBoardMembers_019eb852-e02f-7f23-9c6b-6e47810837e4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LossContingencyPlaintiffTerminatedBoardMembersSuingForReinstatement_019eb852-e02f-7adf-bff1-67edb8e8373d" xlink:href="ago-20260630.xsd#ago_LossContingencyPlaintiffTerminatedBoardMembersSuingForReinstatement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_LossContingencyPlaintiffTerminatedBoardMembersSuingForReinstatement_019eb852-e02f-7adf-bff1-67edb8e8373d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_NumberofDelinquentPayments_019eb852-e02f-7149-acf9-5cb6e4d62875" xlink:href="ago-20260630.xsd#ago_NumberofDelinquentPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_NumberofDelinquentPayments_019eb852-e02f-7149-acf9-5cb6e4d62875" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredPercent_019eb852-e02f-7a58-927b-c0c1c15359cb" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredPercent_019eb852-e02f-7a58-927b-c0c1c15359cb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodtoReachFinalLossSeverityRate_019eb852-e02f-7c7f-8b07-c04404cf9f23" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionsPeriodtoReachFinalLossSeverityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodtoReachFinalLossSeverityRate_019eb852-e02f-7c7f-8b07-c04404cf9f23" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodtoReachIntermediateConditionalDefaultRate_019eb852-e02f-72b9-a64a-17eb20068161" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionsPeriodtoReachIntermediateConditionalDefaultRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodtoReachIntermediateConditionalDefaultRate_019eb852-e02f-72b9-a64a-17eb20068161" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodConditionalDefaultRateHeldConstant_019fd270-0afb-770c-bcaa-51e515d0025d" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionsPeriodConditionalDefaultRateHeldConstant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodConditionalDefaultRateHeldConstant_019fd270-0afb-770c-bcaa-51e515d0025d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionsIncreaseDecreaseinExpectedLosstobePaidNet_019eb852-e02f-7f93-8bb7-093ea0450641" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionsIncreaseDecreaseinExpectedLosstobePaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionsIncreaseDecreaseinExpectedLosstobePaidNet_019eb852-e02f-7f93-8bb7-093ea0450641" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredLeastStressfulEnvironmentPercent_019eb852-e02f-708c-a1bd-e3249d388b51" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredLeastStressfulEnvironmentPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredLeastStressfulEnvironmentPercent_019eb852-e02f-708c-a1bd-e3249d388b51" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionsConditionalDefaultRatePlateauRateProjectionPeriod_019eb852-e02f-7059-800a-3b89b1fd82d3" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionsConditionalDefaultRatePlateauRateProjectionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionsConditionalDefaultRatePlateauRateProjectionPeriod_019eb852-e02f-7059-800a-3b89b1fd82d3" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LossEstimateSensitivityAnalysisChangeInEstimateForIncreasedConditionalDefaultRatePlateauPeriod_019eb852-e02f-7c97-96c7-06b3f95520b5" xlink:href="ago-20260630.xsd#ago_LossEstimateSensitivityAnalysisChangeInEstimateForIncreasedConditionalDefaultRatePlateauPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_LossEstimateSensitivityAnalysisChangeInEstimateForIncreasedConditionalDefaultRatePlateauPeriod_019eb852-e02f-7c97-96c7-06b3f95520b5" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_RecoveryEstimateSensitivityAnalysisChangeInEstimateForDecreasedConditionalDefaultRateRampDownPeriod_019eb852-e02f-7a95-93d1-852f2caae11b" xlink:href="ago-20260630.xsd#ago_RecoveryEstimateSensitivityAnalysisChangeInEstimateForDecreasedConditionalDefaultRateRampDownPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_RecoveryEstimateSensitivityAnalysisChangeInEstimateForDecreasedConditionalDefaultRateRampDownPeriod_019eb852-e02f-7a95-93d1-852f2caae11b" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodOfConsistentConditionalDefaultRate_019eb852-e02f-7564-9b1b-dbef960d67cf" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionsPeriodOfConsistentConditionalDefaultRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7b25-8c36-b3fffadbc439" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionsPeriodOfConsistentConditionalDefaultRate_019eb852-e02f-7564-9b1b-dbef960d67cf" xlink:type="arc" order="19"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredNetExpectedLosstobePaidRecoveredandNetEconomicLossDevelopmentBenefitbyAccountingModelDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ExpectedLosstobePaidRecoveredNetExpectedLosstobePaidRecoveredandNetEconomicLossDevelopmentBenefitbyAccountingModelDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredNetExpectedLosstobePaidRecoveredandNetEconomicLossDevelopmentBenefitbyAccountingModelDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7613-8fb7-b37708365be0" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-73eb-87b1-bbf69307addd" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7613-8fb7-b37708365be0" xlink:to="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-73eb-87b1-bbf69307addd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_019eb852-e02f-7ada-a503-de7b888aca88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-73eb-87b1-bbf69307addd" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_019eb852-e02f-7ada-a503-de7b888aca88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7ada-a503-de7b888aca88_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_019eb852-e02f-7ada-a503-de7b888aca88" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7ada-a503-de7b888aca88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7e4f-91e2-f6040d87a1a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_019eb852-e02f-7ada-a503-de7b888aca88" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7e4f-91e2-f6040d87a1a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuranceContractsMember_019eb852-e02f-70d6-88e0-d0280d25934c" xlink:href="ago-20260630.xsd#ago_InsuranceContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7e4f-91e2-f6040d87a1a3" xlink:to="loc_ago_InsuranceContractsMember_019eb852-e02f-70d6-88e0-d0280d25934c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeVariableInterestEntitiesMember_019eb852-e02f-71a6-aa50-d5934379c535" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7e4f-91e2-f6040d87a1a3" xlink:to="loc_ago_FinancialGuaranteeVariableInterestEntitiesMember_019eb852-e02f-71a6-aa50-d5934379c535" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeAccountedforasCreditDerivativesMember_019eb852-e02f-7660-9a05-c791600d2960" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeAccountedforasCreditDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_019eb852-e02f-7e4f-91e2-f6040d87a1a3" xlink:to="loc_ago_FinancialGuaranteeAccountedforasCreditDerivativesMember_019eb852-e02f-7660-9a05-c791600d2960" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7e93-85ed-3a3f865a7906" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7613-8fb7-b37708365be0" xlink:to="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7e93-85ed-3a3f865a7906" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7a55-ad23-355c65740ea2" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7613-8fb7-b37708365be0" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7a55-ad23-355c65740ea2" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredNetExpectedLosstobePaidAfterNetExpectedRecoveriesforBreachesofRWRollforwardDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ExpectedLosstobePaidRecoveredNetExpectedLosstobePaidAfterNetExpectedRecoveriesforBreachesofRWRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredNetExpectedLosstobePaidAfterNetExpectedRecoveriesforBreachesofRWRollforwardDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7a9e-bfa7-413e561200b8" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7436-9502-c7a1354f9128" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7a9e-bfa7-413e561200b8" xlink:to="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7436-9502-c7a1354f9128" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e02f-76ad-abb5-64c64eb17b13" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7436-9502-c7a1354f9128" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e02f-76ad-abb5-64c64eb17b13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e02f-76ad-abb5-64c64eb17b13_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e02f-76ad-abb5-64c64eb17b13" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e02f-76ad-abb5-64c64eb17b13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7835-b256-825951876880" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e02f-76ad-abb5-64c64eb17b13" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7835-b256-825951876880" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e02f-7daf-8d02-6485257e52c8" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7835-b256-825951876880" xlink:to="loc_country_US_019eb852-e02f-7daf-8d02-6485257e52c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019eb852-e02f-75a7-9c74-f661a3afdaaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7835-b256-825951876880" xlink:to="loc_us-gaap_NonUsMember_019eb852-e02f-75a7-9c74-f661a3afdaaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb852-e02f-7dbd-ad0b-ef9131fa710a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7436-9502-c7a1354f9128" xlink:to="loc_srt_RangeAxis_019eb852-e02f-7dbd-ad0b-ef9131fa710a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e02f-7dbd-ad0b-ef9131fa710a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb852-e02f-7dbd-ad0b-ef9131fa710a" xlink:to="loc_srt_RangeMember_019eb852-e02f-7dbd-ad0b-ef9131fa710a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e02f-7bdf-852f-b864963e6075" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb852-e02f-7dbd-ad0b-ef9131fa710a" xlink:to="loc_srt_RangeMember_019eb852-e02f-7bdf-852f-b864963e6075" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb852-e02f-7338-880a-e24ad166314d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7bdf-852f-b864963e6075" xlink:to="loc_srt_MinimumMember_019eb852-e02f-7338-880a-e24ad166314d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb852-e02f-77f1-94da-777762731cca" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7bdf-852f-b864963e6075" xlink:to="loc_srt_MaximumMember_019eb852-e02f-77f1-94da-777762731cca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_019eb852-e02f-7d53-83c3-280402d9a8d5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7bdf-852f-b864963e6075" xlink:to="loc_srt_WeightedAverageMember_019eb852-e02f-7d53-83c3-280402d9a8d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-76e1-bf9e-a2ef50ca3249" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7436-9502-c7a1354f9128" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-76e1-bf9e-a2ef50ca3249" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-76e1-bf9e-a2ef50ca3249_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-76e1-bf9e-a2ef50ca3249" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-76e1-bf9e-a2ef50ca3249_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-775b-826c-8dc9dea6b220" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-76e1-bf9e-a2ef50ca3249" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-775b-826c-8dc9dea6b220" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-e02f-78f6-a4c7-687c3b0930cd" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-775b-826c-8dc9dea6b220" xlink:to="loc_ago_PublicFinanceMember_019eb852-e02f-78f6-a4c7-687c3b0930cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e02f-78cd-9555-34021dbc7deb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-775b-826c-8dc9dea6b220" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e02f-78cd-9555-34021dbc7deb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherStructuredFinanceMember_019eb852-e02f-7551-96e0-da288e0226ac" xlink:href="ago-20260630.xsd#ago_OtherStructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-775b-826c-8dc9dea6b220" xlink:to="loc_ago_OtherStructuredFinanceMember_019eb852-e02f-7551-96e0-da288e0226ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-e02f-71a9-b58d-8c1531933804" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-775b-826c-8dc9dea6b220" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-e02f-71a9-b58d-8c1531933804" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:href="ago-20260630.xsd#ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7a9e-bfa7-413e561200b8" xlink:to="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7e91-ba6b-921b74a70a0e" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:to="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7e91-ba6b-921b74a70a0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesAccretionOfDiscount_019eb852-e02f-7789-8418-f1ceb220bd71" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesAccretionOfDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesAccretionOfDiscount_019eb852-e02f-7789-8418-f1ceb220bd71" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInDiscountRates_019eb852-e02f-7b9a-83f8-b8e6c5a76f12" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInDiscountRates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInDiscountRates_019eb852-e02f-7b9a-83f8-b8e6c5a76f12" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInTimingAndAssumptions_019eb852-e02f-74ad-964e-938950aec113" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInTimingAndAssumptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInTimingAndAssumptions_019eb852-e02f-74ad-964e-938950aec113" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7fe2-86b1-24a0c502b0f2" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7fe2-86b1-24a0c502b0f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-775d-845b-b197374d4e3f" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PresentValueOfNetExpectedLossAndLossAdjustmentExpensesToBePaidRollForward_019eb852-e02f-7da1-acb0-bcfae360ae13" xlink:to="loc_ago_GuarantorObligationsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-775d-845b-b197374d4e3f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7666-be7a-b9dce8590624" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsClaimLiabilityRiskFreeDiscountRate_019eb852-e02f-7df5-bc18-bda7487cb4a5" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsClaimLiabilityRiskFreeDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7a9e-bfa7-413e561200b8" xlink:to="loc_ago_InsuredFinancialObligationsClaimLiabilityRiskFreeDiscountRate_019eb852-e02f-7df5-bc18-bda7487cb4a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ReinsuranceRecoverablesPeriodafterEndofReportingPeriodforSettlementofCededPaidLosses_019eb852-e02f-74ca-b263-cb5423d64d27" xlink:href="ago-20260630.xsd#ago_ReinsuranceRecoverablesPeriodafterEndofReportingPeriodforSettlementofCededPaidLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7a9e-bfa7-413e561200b8" xlink:to="loc_ago_ReinsuranceRecoverablesPeriodafterEndofReportingPeriodforSettlementofCededPaidLosses_019eb852-e02f-74ca-b263-cb5423d64d27" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredNetEconomicLossDevelopmentBenefitDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ExpectedLosstobePaidRecoveredNetEconomicLossDevelopmentBenefitDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ExpectedLosstobePaidRecoveredNetEconomicLossDevelopmentBenefitDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:href="ago-20260630.xsd#ago_ScheduleofExpectedLossestobePaidTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7501-b79d-1315e0230988" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7501-b79d-1315e0230988" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-7501-b79d-1315e0230988_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7501-b79d-1315e0230988" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-7501-b79d-1315e0230988_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-762a-8155-2f451725a73b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e02f-7501-b79d-1315e0230988" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-762a-8155-2f451725a73b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e02f-73c9-8ed3-2b1d213b81bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e02f-762a-8155-2f451725a73b" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e02f-73c9-8ed3-2b1d213b81bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e02f-72a6-8d2d-e09e459e448c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e02f-72a6-8d2d-e09e459e448c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e02f-72a6-8d2d-e09e459e448c_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e02f-72a6-8d2d-e09e459e448c" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e02f-72a6-8d2d-e09e459e448c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7721-8b5e-e02301cdfb19" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e02f-72a6-8d2d-e09e459e448c" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7721-8b5e-e02301cdfb19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e02f-7b15-a2d2-2a8e103f4fe7" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e02f-7721-8b5e-e02301cdfb19" xlink:to="loc_country_US_019eb852-e02f-7b15-a2d2-2a8e103f4fe7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7ede-b16b-53b97dd58d1d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7ede-b16b-53b97dd58d1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-7ede-b16b-53b97dd58d1d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7ede-b16b-53b97dd58d1d" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-7ede-b16b-53b97dd58d1d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-723e-9769-57531271160f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateLoanCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis_019eb852-e02f-7ede-b16b-53b97dd58d1d" xlink:to="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-723e-9769-57531271160f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FirstMortgageMember_019eb852-e02f-79cf-ba77-48ed729b18dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FirstMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-723e-9769-57531271160f" xlink:to="loc_us-gaap_FirstMortgageMember_019eb852-e02f-79cf-ba77-48ed729b18dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecondMortgageMember_019eb852-e02f-7ad4-a28b-cf0d316956ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecondMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateLoanCategoryDomain_019eb852-e02f-723e-9769-57531271160f" xlink:to="loc_us-gaap_SecondMortgageMember_019eb852-e02f-7ad4-a28b-cf0d316956ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb852-e02f-7e9e-8d30-29afcc0145fa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:to="loc_srt_RangeAxis_019eb852-e02f-7e9e-8d30-29afcc0145fa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e02f-7e9e-8d30-29afcc0145fa_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb852-e02f-7e9e-8d30-29afcc0145fa" xlink:to="loc_srt_RangeMember_019eb852-e02f-7e9e-8d30-29afcc0145fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e02f-7abe-b03d-4e936c47143f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb852-e02f-7e9e-8d30-29afcc0145fa" xlink:to="loc_srt_RangeMember_019eb852-e02f-7abe-b03d-4e936c47143f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb852-e02f-7d8b-9097-f9162f2acadb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7abe-b03d-4e936c47143f" xlink:to="loc_srt_MinimumMember_019eb852-e02f-7d8b-9097-f9162f2acadb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb852-e02f-70a7-bc85-40a0946f43a5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7abe-b03d-4e936c47143f" xlink:to="loc_srt_MaximumMember_019eb852-e02f-70a7-bc85-40a0946f43a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_019eb852-e02f-73fb-b94b-ce6de9152653" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7abe-b03d-4e936c47143f" xlink:to="loc_srt_WeightedAverageMember_019eb852-e02f-73fb-b94b-ce6de9152653" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7412-9998-e5dc3eccb3ab" xlink:href="ago-20260630.xsd#ago_DeferredLoanRecoveryScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidTable_019eb852-e02f-7d8a-b669-30a1dd543a74" xlink:to="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7412-9998-e5dc3eccb3ab" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7412-9998-e5dc3eccb3ab_default" xlink:href="ago-20260630.xsd#ago_DeferredLoanRecoveryScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7412-9998-e5dc3eccb3ab" xlink:to="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-7412-9998-e5dc3eccb3ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-79ce-afb4-e7f09fe124bf" xlink:href="ago-20260630.xsd#ago_DeferredLoanRecoveryScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ago_DeferredLoanRecoveryScenarioAxis_019eb852-e02f-7412-9998-e5dc3eccb3ab" xlink:to="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-79ce-afb4-e7f09fe124bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BaseScenarioMember_019eb852-e02f-7528-918d-59448697d959" xlink:href="ago-20260630.xsd#ago_BaseScenarioMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DeferredLoanRecoveryScenarioDomain_019eb852-e02f-79ce-afb4-e7f09fe124bf" xlink:to="loc_ago_BaseScenarioMember_019eb852-e02f-7528-918d-59448697d959" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7f96-a5bc-800184c5a548" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-7f96-a5bc-800184c5a548" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-74fd-bb65-ac546c3f058b" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties_019eb852-e02f-74fd-bb65-ac546c3f058b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInDiscountRates_019eb852-e02f-725d-a084-ed4714cd75b0" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInDiscountRates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarrantiesChangesInDiscountRates_019eb852-e02f-725d-a084-ed4714cd75b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossToBePaidAfterRecoveriesForRepresentationsAndWarrantiesDiscountRate_019eb852-e02f-7f70-bb42-92bd2e0d1d98" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossToBePaidAfterRecoveriesForRepresentationsAndWarrantiesDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossToBePaidAfterRecoveriesForRepresentationsAndWarrantiesDiscountRate_019eb852-e02f-7f70-bb42-92bd2e0d1d98" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLossToBePaidAfterRecoveriesForRepresentationsAndWarrantiesWeightedAverageDiscountRate_019eb852-e02f-7d57-9345-ea37875ea903" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLossToBePaidAfterRecoveriesForRepresentationsAndWarrantiesWeightedAverageDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_GuarantorObligationsNetExpectedLossToBePaidAfterRecoveriesForRepresentationsAndWarrantiesWeightedAverageDiscountRate_019eb852-e02f-7d57-9345-ea37875ea903" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredPercent_019eb852-e02f-76a0-80fc-9c0d4b767383" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleofExpectedLossestobePaidLineItems_019eb852-e02f-7ad2-bb4d-f337b5fc98bf" xlink:to="loc_ago_GuarantorObligationsProjectedLossAssumptionDeferredLoanBalancesToBeRecoveredPercent_019eb852-e02f-76a0-80fc-9c0d4b767383" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e02f-7010-8136-94f0beadb347" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e02f-7789-b962-21d13079cdc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e02f-7010-8136-94f0beadb347" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e02f-7789-b962-21d13079cdc8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019eb852-e02f-7d2a-8d11-85abd5120699" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e02f-7789-b962-21d13079cdc8" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019eb852-e02f-7d2a-8d11-85abd5120699" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019eb852-e02f-7d2a-8d11-85abd5120699_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019eb852-e02f-7d2a-8d11-85abd5120699" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019eb852-e02f-7d2a-8d11-85abd5120699_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019eb852-e02f-7402-88b9-77527e50c24b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019eb852-e02f-7d2a-8d11-85abd5120699" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019eb852-e02f-7402-88b9-77527e50c24b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ForeignCurrencyConcentrationRiskMember_019eb852-e02f-70da-b9a2-822347c08866" xlink:href="ago-20260630.xsd#ago_ForeignCurrencyConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019eb852-e02f-7402-88b9-77527e50c24b" xlink:to="loc_ago_ForeignCurrencyConcentrationRiskMember_019eb852-e02f-70da-b9a2-822347c08866" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019eb852-e02f-7354-b764-97805c295634" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e02f-7789-b962-21d13079cdc8" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019eb852-e02f-7354-b764-97805c295634" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019eb852-e02f-7354-b764-97805c295634_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019eb852-e02f-7354-b764-97805c295634" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019eb852-e02f-7354-b764-97805c295634_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019eb852-e02f-7e9f-8cb5-9b12d9f27b92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019eb852-e02f-7354-b764-97805c295634" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019eb852-e02f-7e9f-8cb5-9b12d9f27b92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsReceivableMember_019eb852-e02f-7984-97b3-2297c5deefb5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019eb852-e02f-7e9f-8cb5-9b12d9f27b92" xlink:to="loc_us-gaap_PremiumsReceivableMember_019eb852-e02f-7984-97b3-2297c5deefb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e02f-7aa2-96a7-40f809c5e2d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e02f-7789-b962-21d13079cdc8" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e02f-7aa2-96a7-40f809c5e2d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e02f-7aa2-96a7-40f809c5e2d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e02f-7aa2-96a7-40f809c5e2d7" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e02f-7aa2-96a7-40f809c5e2d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e02f-704c-8b16-d3d6ea1613f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e02f-7aa2-96a7-40f809c5e2d7" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e02f-704c-8b16-d3d6ea1613f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsReceivableMember_019eb852-e02f-70ef-b34b-c237d1c59ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e02f-704c-8b16-d3d6ea1613f3" xlink:to="loc_us-gaap_PremiumsReceivableMember_019eb852-e02f-70ef-b34b-c237d1c59ff3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb852-e02f-7f78-a151-4117203c8ab1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e02f-7789-b962-21d13079cdc8" xlink:to="loc_srt_RangeAxis_019eb852-e02f-7f78-a151-4117203c8ab1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e02f-7f78-a151-4117203c8ab1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb852-e02f-7f78-a151-4117203c8ab1" xlink:to="loc_srt_RangeMember_019eb852-e02f-7f78-a151-4117203c8ab1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e02f-7d0e-a039-38a160c85d86" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb852-e02f-7f78-a151-4117203c8ab1" xlink:to="loc_srt_RangeMember_019eb852-e02f-7d0e-a039-38a160c85d86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb852-e02f-74ce-aca1-05fcf8004747" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7d0e-a039-38a160c85d86" xlink:to="loc_srt_MinimumMember_019eb852-e02f-74ce-aca1-05fcf8004747" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb852-e02f-74be-8625-51b650dabff0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e02f-7d0e-a039-38a160c85d86" xlink:to="loc_srt_MaximumMember_019eb852-e02f-74be-8625-51b650dabff0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019eb852-e02f-71d3-8a05-fdb43dc46301" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e02f-7010-8136-94f0beadb347" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019eb852-e02f-71d3-8a05-fdb43dc46301" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityWeightedAverageRiskFreeDiscountRate_019eb852-e02f-7490-965b-6dd24d3a96b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityWeightedAverageRiskFreeDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e02f-7010-8136-94f0beadb347" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityWeightedAverageRiskFreeDiscountRate_019eb852-e02f-7490-965b-6dd24d3a96b7" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceExpectedFuturePremiumCollectionsandEarningsDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceExpectedFuturePremiumCollectionsandEarningsDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceExpectedFuturePremiumCollectionsandEarningsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-75b6-964c-73944e36e552" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsurancePremiumsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e02f-7d8d-b6c0-a236469443a2" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsurancePremiumsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-75b6-964c-73944e36e552" xlink:to="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e02f-7d8d-b6c0-a236469443a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e02f-7b55-a6c2-47f7941d9a7e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e02f-7d8d-b6c0-a236469443a2" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e02f-7b55-a6c2-47f7941d9a7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e02f-7b55-a6c2-47f7941d9a7e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e02f-7b55-a6c2-47f7941d9a7e" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e02f-7b55-a6c2-47f7941d9a7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7cdc-a974-f77735c85dd9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e02f-7b55-a6c2-47f7941d9a7e" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7cdc-a974-f77735c85dd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceSegmentMember_019eb852-e030-7676-b719-e287247a9b2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7cdc-a974-f77735c85dd9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceSegmentMember_019eb852-e030-7676-b719-e287247a9b2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-722f-9da0-68ecd95a702b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e02f-7d8d-b6c0-a236469443a2" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-722f-9da0-68ecd95a702b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-722f-9da0-68ecd95a702b_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-722f-9da0-68ecd95a702b" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-722f-9da0-68ecd95a702b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-7d3c-a010-a1ea5c2dad57" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-722f-9da0-68ecd95a702b" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-7d3c-a010-a1ea5c2dad57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember_019eb852-e030-7318-b8b5-b089f8b6eab9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-7d3c-a010-a1ea5c2dad57" xlink:to="loc_srt_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember_019eb852-e030-7318-b8b5-b089f8b6eab9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:href="ago-20260630.xsd#ago_FuturePremiumsToBeCollectedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-75b6-964c-73944e36e552" xlink:to="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedDuringThirdQuarterFollowingBalanceSheetDate_019eb852-e030-7208-a2e1-33dc8afcaa74" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedDuringThirdQuarterFollowingBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedDuringThirdQuarterFollowingBalanceSheetDate_019eb852-e030-7208-a2e1-33dc8afcaa74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedDuringFourthQuarterFollowingBalanceSheetDate_019eb852-e030-7d29-a8d8-3b2fb553abfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedDuringFourthQuarterFollowingBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedDuringFourthQuarterFollowingBalanceSheetDate_019eb852-e030-7d29-a8d8-3b2fb553abfe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedWithinOneYearFromBalanceSheetDate_019eb852-e030-7663-8789-b48535ff8bd3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedWithinOneYearFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedWithinOneYearFromBalanceSheetDate_019eb852-e030-7663-8789-b48535ff8bd3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate_019eb852-e030-7b09-b10c-e13a2b905b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate_019eb852-e030-7b09-b10c-e13a2b905b3b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate_019eb852-e030-732e-8cd5-fbd82bb8f0c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate_019eb852-e030-732e-8cd5-fbd82bb8f0c2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate_019eb852-e030-7f21-915b-a57586cb392d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate_019eb852-e030-7f21-915b-a57586cb392d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate_019eb852-e030-76de-bbe5-337399d0afd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate_019eb852-e030-76de-bbe5-337399d0afd2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFiveAndWithin10YearsFromBalanceSheetDate_019eb852-e030-71ca-8ebd-5e2b14a2a38b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFiveAndWithin10YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFiveAndWithin10YearsFromBalanceSheetDate_019eb852-e030-71ca-8ebd-5e2b14a2a38b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan10AndWithin15YearsFromBalanceSheetDate_019eb852-e030-7020-8ed0-d382bc053bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan10AndWithin15YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan10AndWithin15YearsFromBalanceSheetDate_019eb852-e030-7020-8ed0-d382bc053bcf" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan15AndWithin20YearsFromBalanceSheetDate_019eb852-e030-7207-b098-d7b2cda41885" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan15AndWithin20YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan15AndWithin20YearsFromBalanceSheetDate_019eb852-e030-7207-b098-d7b2cda41885" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan20AndWithin25YearsFromBalanceSheetDate_019eb852-e030-76ef-a694-063774c1f800" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan20AndWithin25YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan20AndWithin25YearsFromBalanceSheetDate_019eb852-e030-76ef-a694-063774c1f800" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan25AndWithin30YearsFromBalanceSheetDate_019eb852-e030-7bc9-a3cc-52161b8004e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan25AndWithin30YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan25AndWithin30YearsFromBalanceSheetDate_019eb852-e030-7bc9-a3cc-52161b8004e2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan30AndWithin35YearsFromBalanceSheetDate_019eb852-e030-78d4-864b-b81cb7e44acd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan30AndWithin35YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan30AndWithin35YearsFromBalanceSheetDate_019eb852-e030-78d4-864b-b81cb7e44acd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivablePremiumExpectedToBeCollected_019eb852-e030-7cee-b973-3ead3f7766d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivablePremiumExpectedToBeCollected"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FuturePremiumsToBeCollectedAbstract_019eb852-e030-7f82-bb8a-c9ba1187f9e9" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivablePremiumExpectedToBeCollected_019eb852-e030-7cee-b973-3ead3f7766d0" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:href="ago-20260630.xsd#ago_FutureNetPremiumsToBeEarnedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-75b6-964c-73944e36e552" xlink:to="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedDuringThirdQuarterFollowingBalanceSheetDate_019eb852-e030-712b-a5cd-ab758866a105" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedDuringThirdQuarterFollowingBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedDuringThirdQuarterFollowingBalanceSheetDate_019eb852-e030-712b-a5cd-ab758866a105" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedDuringFourthQuarterFollowingBalanceSheetDate_019eb852-e030-776b-b74a-458a46afc167" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedDuringFourthQuarterFollowingBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedDuringFourthQuarterFollowingBalanceSheetDate_019eb852-e030-776b-b74a-458a46afc167" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedFiscalYear_019eb852-e030-72f6-9599-dcaaa4fe3d34" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedFiscalYear_019eb852-e030-72f6-9599-dcaaa4fe3d34" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate_019eb852-e030-7ef9-9fc0-59f87566d337" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate_019eb852-e030-7ef9-9fc0-59f87566d337" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate_019eb852-e030-7344-a03b-499dc2ccc1a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate_019eb852-e030-7344-a03b-499dc2ccc1a7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate_019eb852-e030-7648-bd01-3ed3d53fbc4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate_019eb852-e030-7648-bd01-3ed3d53fbc4b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate_019eb852-e030-783e-b96b-e0ed378ba343" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate_019eb852-e030-783e-b96b-e0ed378ba343" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanFiveAndWithin10YearsFromBalanceSheetDate_019eb852-e030-73c9-b82d-6361f7b57656" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanFiveAndWithin10YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThanFiveAndWithin10YearsFromBalanceSheetDate_019eb852-e030-73c9-b82d-6361f7b57656" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan10AndWithin15YearsFromBalanceSheetDate_019eb852-e030-71e4-a691-dcf9c8bde898" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan10AndWithin15YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan10AndWithin15YearsFromBalanceSheetDate_019eb852-e030-71e4-a691-dcf9c8bde898" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan15AndWithin20YearsFromBalanceSheetDate_019eb852-e030-7916-94fe-443182072056" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan15AndWithin20YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan15AndWithin20YearsFromBalanceSheetDate_019eb852-e030-7916-94fe-443182072056" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan20AndWithin25YearsFromBalanceSheetDate_019eb852-e030-7f7c-b385-c2073c17888f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan20AndWithin25YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan20AndWithin25YearsFromBalanceSheetDate_019eb852-e030-7f7c-b385-c2073c17888f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan25AndWithin30YearsFromBalanceSheetDate_019eb852-e030-7ee6-b942-79dec9021acb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan25AndWithin30YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan25AndWithin30YearsFromBalanceSheetDate_019eb852-e030-7ee6-b942-79dec9021acb" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan30AndWithin35YearsFromBalanceSheetDate_019eb852-e030-72a3-a03c-a3c3e008485b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan30AndWithin35YearsFromBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedMoreThan30AndWithin35YearsFromBalanceSheetDate_019eb852-e030-72a3-a03c-a3c3e008485b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsUnearnedPremiumRevenueExcludingClaimsPaidNotYetExpensedNet_019eb852-e030-76eb-911c-27c0370b42a9" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsUnearnedPremiumRevenueExcludingClaimsPaidNotYetExpensedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FutureNetPremiumsToBeEarnedAbstract_019eb852-e030-7066-86f8-f1b7f76914e3" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsUnearnedPremiumRevenueExcludingClaimsPaidNotYetExpensedNet_019eb852-e030-76eb-911c-27c0370b42a9" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:href="ago-20260630.xsd#ago_PremiumsReceivableAccretionOfDiscountAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-75b6-964c-73944e36e552" xlink:to="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableThirdQuarter_019eb852-e030-735f-994f-bcab5c19ab0e" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableThirdQuarter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableThirdQuarter_019eb852-e030-735f-994f-bcab5c19ab0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableFourthQuarter_019eb852-e030-704c-bf4a-091e6e2442de" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableFourthQuarter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableFourthQuarter_019eb852-e030-704c-bf4a-091e6e2442de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearOne_019eb852-e030-7c2f-9935-8154774b3f5c" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearOne_019eb852-e030-7c2f-9935-8154774b3f5c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearTwo_019eb852-e030-74c5-8624-b0e299dcdafb" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearTwo_019eb852-e030-74c5-8624-b0e299dcdafb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearThree_019eb852-e030-70c0-9474-178288a0273a" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearThree_019eb852-e030-70c0-9474-178288a0273a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearFour_019eb852-e030-7d85-82ab-36c6d843881a" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearFour_019eb852-e030-7d85-82ab-36c6d843881a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearFive_019eb852-e030-76e4-8a9e-88ca45b4a3be" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYearFive_019eb852-e030-76e4-8a9e-88ca45b4a3be" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear5Through10_019eb852-e030-72db-8909-49aa6492c9c5" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear5Through10"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear5Through10_019eb852-e030-72db-8909-49aa6492c9c5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear10Through15_019eb852-e030-7cdf-9010-873db0fbfd1a" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear10Through15"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear10Through15_019eb852-e030-7cdf-9010-873db0fbfd1a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear15Through20_019eb852-e030-7894-9ab4-4a2c46fd0ab0" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear15Through20"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear15Through20_019eb852-e030-7894-9ab4-4a2c46fd0ab0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear20Through25_019eb852-e030-7021-81f6-e197391e50cb" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear20Through25"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear20Through25_019eb852-e030-7021-81f6-e197391e50cb" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear25Through30_019eb852-e030-7e06-b269-428f582212ec" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear25Through30"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear25Through30_019eb852-e030-7e06-b269-428f582212ec" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear30Through35_019eb852-e030-7aa7-89cb-04b4ae25b3b6" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear30Through35"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableYear30Through35_019eb852-e030-7aa7-89cb-04b4ae25b3b6" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableTotal_019eb852-e030-766d-83c8-5ae9d9d8eb5a" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableTotal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_PremiumsReceivableAccretionOfDiscountAbstract_019eb852-e030-7463-8337-75b42f7047f6" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPremiumsReceivableAdjustmentAccretionOfDiscountOnPremiumReceivableTotal_019eb852-e030-766d-83c8-5ae9d9d8eb5a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:href="ago-20260630.xsd#ago_EarningsOfDeferredPremiumRevenueNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-75b6-964c-73944e36e552" xlink:to="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetThirdQuarter_019eb852-e030-72b0-917f-72d38cd0072a" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetThirdQuarter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetThirdQuarter_019eb852-e030-72b0-917f-72d38cd0072a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetFourthQuarter_019eb852-e030-77ff-9029-3f44acdc295c" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetFourthQuarter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetFourthQuarter_019eb852-e030-77ff-9029-3f44acdc295c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedNetFiscalYear_019eb852-e030-7cde-b453-1628acd350fd" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedNetFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedNetFiscalYear_019eb852-e030-7cde-b453-1628acd350fd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearTwo_019eb852-e030-7aa6-a9ee-9f4f3f3a8fc2" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearTwo_019eb852-e030-7aa6-a9ee-9f4f3f3a8fc2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearThree_019eb852-e030-712f-8b94-ee5363e3c1a0" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearThree_019eb852-e030-712f-8b94-ee5363e3c1a0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearFour_019eb852-e030-7977-a811-a4cc4b6313e4" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearFour_019eb852-e030-7977-a811-a4cc4b6313e4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearFive_019eb852-e030-7df1-ae70-5aadaae888a7" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetYearFive_019eb852-e030-7df1-ae70-5aadaae888a7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear5Through10_019eb852-e030-758c-b6d2-c65df9e261f2" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear5Through10"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear5Through10_019eb852-e030-758c-b6d2-c65df9e261f2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear10Through15_019eb852-e030-73bd-b50d-1bc8b05f1287" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear10Through15"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear10Through15_019eb852-e030-73bd-b50d-1bc8b05f1287" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear15Through20_019eb852-e030-73d4-bd38-16ba4120366e" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear15Through20"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear15Through20_019eb852-e030-73d4-bd38-16ba4120366e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear20Through25_019eb852-e030-7086-9206-7c890976db39" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear20Through25"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear20Through25_019eb852-e030-7086-9206-7c890976db39" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear25Through30_019eb852-e030-7519-92ef-61020e54a7e2" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear25Through30"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear25Through30_019eb852-e030-7519-92ef-61020e54a7e2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear30Through35_019eb852-e030-72a6-86a9-83d8bc7cb56d" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear30Through35"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractPremiumRevenueToBeRecognizedNetAfterYear30Through35_019eb852-e030-72a6-86a9-83d8bc7cb56d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedNet_019eb852-e030-70b2-af9f-3383b16a055d" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_EarningsOfDeferredPremiumRevenueNetAbstract_019eb852-e030-73c8-9c9e-90a55b82ad06" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenueToBeRecognizedNet_019eb852-e030-70b2-af9f-3383b16a055d" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceSelectedInformationforPoliciesPaidInInstallmentsDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceSelectedInformationforPoliciesPaidInInstallmentsDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceSelectedInformationforPoliciesPaidInInstallmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-7d4a-a64f-7e4b62f8a647" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsurancePremiumsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e030-7af7-bedb-721faa9eef80" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsurancePremiumsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-7d4a-a64f-7e4b62f8a647" xlink:to="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e030-7af7-bedb-721faa9eef80" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-79f5-9170-adfd6f88f5f9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsTable_019eb852-e030-7af7-bedb-721faa9eef80" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-79f5-9170-adfd6f88f5f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-79f5-9170-adfd6f88f5f9_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-79f5-9170-adfd6f88f5f9" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-79f5-9170-adfd6f88f5f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-70fb-acec-3a809e868f4b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-79f5-9170-adfd6f88f5f9" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-70fb-acec-3a809e868f4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteePoliciesPaidinInstallmentsMember_019eb852-e030-7885-b6d7-3be29189f038" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteePoliciesPaidinInstallmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-70fb-acec-3a809e868f4b" xlink:to="loc_ago_FinancialGuaranteePoliciesPaidinInstallmentsMember_019eb852-e030-7885-b6d7-3be29189f038" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivable_019eb852-e030-79d6-8752-b699d0f8fbf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-7d4a-a64f-7e4b62f8a647" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivable_019eb852-e030-79d6-8752-b699d0f8fbf3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodUnearnedPremiumRevenue_019eb852-e030-7ee8-af0a-d1afe9e73eb5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodUnearnedPremiumRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-7d4a-a64f-7e4b62f8a647" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodUnearnedPremiumRevenue_019eb852-e030-7ee8-af0a-d1afe9e73eb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageRiskFreeDiscountRate_019eb852-e030-77cd-8cc1-513b3e235e77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageRiskFreeDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-7d4a-a64f-7e4b62f8a647" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageRiskFreeDiscountRate_019eb852-e030-77cd-8cc1-513b3e235e77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageCollectionPeriod1_019eb852-e030-7be9-9c76-ff2213fdc572" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageCollectionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuaranteeInsurancePremiumsLineItems_019eb852-e030-7d4a-a64f-7e4b62f8a647" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageCollectionPeriod1_019eb852-e030-7be9-9c76-ff2213fdc572" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceLossandLAEReserveandSalvageandSubrogationRecoverableNetofReinsuranceDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceLossandLAEReserveandSalvageandSubrogationRecoverableNetofReinsuranceDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceLossandLAEReserveandSalvageandSubrogationRecoverableNetofReinsuranceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems_019eb852-e030-7685-8264-41b27a82be84" xlink:href="ago-20260630.xsd#ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-70ab-a8bc-1c90fa9ad86a" xlink:href="ago-20260630.xsd#ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems_019eb852-e030-7685-8264-41b27a82be84" xlink:to="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-70ab-a8bc-1c90fa9ad86a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e030-7d31-b003-a7ccb9ff6aa5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-70ab-a8bc-1c90fa9ad86a" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e030-7d31-b003-a7ccb9ff6aa5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e030-7d31-b003-a7ccb9ff6aa5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e030-7d31-b003-a7ccb9ff6aa5" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e030-7d31-b003-a7ccb9ff6aa5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e030-745b-bc14-61016173510a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e030-7d31-b003-a7ccb9ff6aa5" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e030-745b-bc14-61016173510a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e030-7df1-b4a4-9d8e7121ea61" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e030-745b-bc14-61016173510a" xlink:to="loc_country_US_019eb852-e030-7df1-b4a4-9d8e7121ea61" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019eb852-e030-760a-9243-33b948799847" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e030-745b-bc14-61016173510a" xlink:to="loc_us-gaap_NonUsMember_019eb852-e030-760a-9243-33b948799847" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-7a41-8aa6-49b6b9f4285f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-70ab-a8bc-1c90fa9ad86a" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-7a41-8aa6-49b6b9f4285f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7a41-8aa6-49b6b9f4285f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-7a41-8aa6-49b6b9f4285f" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7a41-8aa6-49b6b9f4285f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7634-a13a-1377034c16f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-7a41-8aa6-49b6b9f4285f" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7634-a13a-1377034c16f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-e030-74cc-bd94-13b60975b4b1" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7634-a13a-1377034c16f1" xlink:to="loc_ago_PublicFinanceMember_019eb852-e030-74cc-bd94-13b60975b4b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e030-7468-a894-ab730bbc29a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7634-a13a-1377034c16f1" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e030-7468-a894-ab730bbc29a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherStructuredFinanceMember_019eb852-e030-75c3-b29d-1835ab276618" xlink:href="ago-20260630.xsd#ago_OtherStructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7634-a13a-1377034c16f1" xlink:to="loc_ago_OtherStructuredFinanceMember_019eb852-e030-75c3-b29d-1835ab276618" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-e030-7968-823c-09ceb11c3c03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7634-a13a-1377034c16f1" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-e030-7968-823c-09ceb11c3c03" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-747a-8e70-b8bc74374ac9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-70ab-a8bc-1c90fa9ad86a" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-747a-8e70-b8bc74374ac9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-747a-8e70-b8bc74374ac9_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-747a-8e70-b8bc74374ac9" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-747a-8e70-b8bc74374ac9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-737e-8d78-7056fc23a8b4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-747a-8e70-b8bc74374ac9" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-737e-8d78-7056fc23a8b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceAndOtherProductLineMember_019eb852-e030-73c2-92d9-789e01753a5c" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceAndOtherProductLineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-737e-8d78-7056fc23a8b4" xlink:to="loc_ago_FinancialGuaranteeInsuranceAndOtherProductLineMember_019eb852-e030-73c2-92d9-789e01753a5c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ReserveForLossesAndLossAdjustmentExpensesNetOfReinsuranceAndSalvageAndSubrogationRecoveries_019eb852-e030-7efc-95db-5466de8fd4d0" xlink:href="ago-20260630.xsd#ago_ReserveForLossesAndLossAdjustmentExpensesNetOfReinsuranceAndSalvageAndSubrogationRecoveries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems_019eb852-e030-7685-8264-41b27a82be84" xlink:to="loc_ago_ReserveForLossesAndLossAdjustmentExpensesNetOfReinsuranceAndSalvageAndSubrogationRecoveries_019eb852-e030-7efc-95db-5466de8fd4d0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceReconciliationofNetExpectedLosstobePaidandExpensedDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceReconciliationofNetExpectedLosstobePaidandExpensedDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceReconciliationofNetExpectedLosstobePaidandExpensedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e030-7f26-9257-142f445ff9d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e030-7f26-9257-142f445ff9d9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-7501-9b52-deced078948c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019eb852-e030-7f26-9257-142f445ff9d9" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-7501-9b52-deced078948c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7501-9b52-deced078948c_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-7501-9b52-deced078948c" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7501-9b52-deced078948c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7197-bf3e-50cbe5ed8c73" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-7501-9b52-deced078948c" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7197-bf3e-50cbe5ed8c73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceAndOtherProductLineMember_019eb852-e030-74cf-bdaa-c531acb77849" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceAndOtherProductLineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7197-bf3e-50cbe5ed8c73" xlink:to="loc_ago_FinancialGuaranteeInsuranceAndOtherProductLineMember_019eb852-e030-74cf-bdaa-c531acb77849" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e030-749e-9eec-112ef9b8deb6" xlink:href="ago-20260630.xsd#ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:to="loc_ago_GuarantorObligationsNetExpectedLosstobePaidAfterRecoveriesforRepresentationsandWarranties_019eb852-e030-749e-9eec-112ef9b8deb6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsPaidButUnexpensedLossesNet_019eb852-e030-7cf4-86c6-3d58835ca986" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsPaidButUnexpensedLossesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsPaidButUnexpensedLossesNet_019eb852-e030-7cf4-86c6-3d58835ca986" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsSalvageandSubrogationRecoveriesNet_019eb852-e030-7ff0-9f2c-5478000d2d1c" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsSalvageandSubrogationRecoveriesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsSalvageandSubrogationRecoveriesNet_019eb852-e030-7ff0-9f2c-5478000d2d1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet_019eb852-e030-78ce-a536-60172f0698fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:to="loc_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet_019eb852-e030-78ce-a536-60172f0698fd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceContractsNetLosstobeExpensedPresentValue_019eb852-e030-74a5-a10b-ba84356fe000" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceContractsNetLosstobeExpensedPresentValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019eb852-e030-74bb-93c5-3f355d40cbac" xlink:to="loc_ago_FinancialGuaranteeInsuranceContractsNetLosstobeExpensedPresentValue_019eb852-e030-74a5-a10b-ba84356fe000" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceLossandLAEReportedontheStatementsofOperationsDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceLossandLAEReportedontheStatementsofOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceLossandLAEReportedontheStatementsofOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems_019eb852-e030-7169-9764-dfea7e5b267d" xlink:href="ago-20260630.xsd#ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-786a-a8d1-ad506b94209d" xlink:href="ago-20260630.xsd#ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems_019eb852-e030-7169-9764-dfea7e5b267d" xlink:to="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-786a-a8d1-ad506b94209d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-70b7-9c71-76da3ec4b0d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-786a-a8d1-ad506b94209d" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-70b7-9c71-76da3ec4b0d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-70b7-9c71-76da3ec4b0d3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-70b7-9c71-76da3ec4b0d3" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-70b7-9c71-76da3ec4b0d3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7939-a321-369c313777f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-70b7-9c71-76da3ec4b0d3" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7939-a321-369c313777f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-e030-75e1-8a09-bfba76ce7507" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7939-a321-369c313777f3" xlink:to="loc_ago_PublicFinanceMember_019eb852-e030-75e1-8a09-bfba76ce7507" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e030-7753-aeac-faef5fc9e6c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7939-a321-369c313777f3" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e030-7753-aeac-faef5fc9e6c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherStructuredFinanceMember_019eb852-e030-71ff-9602-e739db47136e" xlink:href="ago-20260630.xsd#ago_OtherStructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7939-a321-369c313777f3" xlink:to="loc_ago_OtherStructuredFinanceMember_019eb852-e030-71ff-9602-e739db47136e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-e030-7d9d-a36c-2b361a5054c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7939-a321-369c313777f3" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-e030-7d9d-a36c-2b361a5054c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-7911-83e5-733a2598237d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-786a-a8d1-ad506b94209d" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-7911-83e5-733a2598237d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7911-83e5-733a2598237d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-7911-83e5-733a2598237d" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7911-83e5-733a2598237d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7b09-aca3-77373dd2aac9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-7911-83e5-733a2598237d" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7b09-aca3-77373dd2aac9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuaranteeInsuranceAndOtherProductLineMember_019eb852-e030-7a00-8baf-d8056ab474d8" xlink:href="ago-20260630.xsd#ago_FinancialGuaranteeInsuranceAndOtherProductLineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7b09-aca3-77373dd2aac9" xlink:to="loc_ago_FinancialGuaranteeInsuranceAndOtherProductLineMember_019eb852-e030-7a00-8baf-d8056ab474d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e030-7f54-834a-394671646ed1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableTable_019eb852-e030-786a-a8d1-ad506b94209d" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e030-7f54-834a-394671646ed1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e030-7f54-834a-394671646ed1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e030-7f54-834a-394671646ed1" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e030-7f54-834a-394671646ed1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e030-77de-bec4-cea84deb8896" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e030-7f54-834a-394671646ed1" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e030-77de-bec4-cea84deb8896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e030-78f1-a2f1-9bb1f6013119" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e030-77de-bec4-cea84deb8896" xlink:to="loc_country_US_019eb852-e030-78f1-a2f1-9bb1f6013119" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019eb852-e030-7e63-9c92-3dea220260a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e030-77de-bec4-cea84deb8896" xlink:to="loc_us-gaap_NonUsMember_019eb852-e030-7e63-9c92-3dea220260a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019eb852-e030-76fe-b0a3-f1076d7c7a67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderBenefitsAndClaimsIncurredNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_LiabilityforClaimsandClaimsAdjustmentExpenseIncludingSalvageandSubrogationRecoverableLineItems_019eb852-e030-7169-9764-dfea7e5b267d" xlink:to="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019eb852-e030-76fe-b0a3-f1076d7c7a67" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceBIGTransactionLossSummaryDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ContractsAccountedforasFinancialGuarantyInsuranceBIGTransactionLossSummaryDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ContractsAccountedforasFinancialGuarantyInsuranceBIGTransactionLossSummaryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityTable_019eb852-e030-7a00-9815-2f18861f41a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityTable_019eb852-e030-7a00-9815-2f18861f41a0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e030-7142-b92c-3bb7669361d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityTable_019eb852-e030-7a00-9815-2f18861f41a0" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e030-7142-b92c-3bb7669361d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e030-7142-b92c-3bb7669361d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e030-7142-b92c-3bb7669361d6" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e030-7142-b92c-3bb7669361d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e030-7499-ae26-d304328893a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019eb852-e030-7142-b92c-3bb7669361d6" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e030-7499-ae26-d304328893a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-e030-7f5e-b193-4597eab36c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InternalNoninvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019eb852-e030-7499-ae26-d304328893a3" xlink:to="loc_us-gaap_InternalNoninvestmentGradeMember_019eb852-e030-7f5e-b193-4597eab36c6d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-7720-be7b-89a272dad52d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityTable_019eb852-e030-7a00-9815-2f18861f41a0" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-7720-be7b-89a272dad52d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-7720-be7b-89a272dad52d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-7720-be7b-89a272dad52d" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-7720-be7b-89a272dad52d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-79a0-ab96-13613a29f0c7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e030-7720-be7b-89a272dad52d" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-79a0-ab96-13613a29f0c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember_019eb852-e030-74ed-a6bb-43e4d272a873" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e030-79a0-ab96-13613a29f0c7" xlink:to="loc_srt_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember_019eb852-e030-74ed-a6bb-43e4d272a873" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-e030-76d8-accb-f89db79bc3ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityTable_019eb852-e030-7a00-9815-2f18861f41a0" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-e030-76d8-accb-f89db79bc3ca" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-76d8-accb-f89db79bc3ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SurveillanceCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-e030-76d8-accb-f89db79bc3ca" xlink:to="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-76d8-accb-f89db79bc3ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-74e5-a533-17d691d7d53b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SurveillanceCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis_019eb852-e030-76d8-accb-f89db79bc3ca" xlink:to="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-74e5-a533-17d691d7d53b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel1Member_019eb852-e030-7eb1-af8d-37296791b6e4" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-74e5-a533-17d691d7d53b" xlink:to="loc_ago_InternalNoninvestmentGradeLevel1Member_019eb852-e030-7eb1-af8d-37296791b6e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel2Member_019eb852-e030-7000-9920-30c61c85b9d4" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-74e5-a533-17d691d7d53b" xlink:to="loc_ago_InternalNoninvestmentGradeLevel2Member_019eb852-e030-7000-9920-30c61c85b9d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InternalNoninvestmentGradeLevel3Member_019eb852-e030-70b0-87f4-5284961abce4" xlink:href="ago-20260630.xsd#ago_InternalNoninvestmentGradeLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SurveillanceCategoryDomain_019eb852-e030-74e5-a533-17d691d7d53b" xlink:to="loc_ago_InternalNoninvestmentGradeLevel3Member_019eb852-e030-70b0-87f4-5284961abce4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfRisksAbstract_019eb852-e030-75f9-801d-d037e314c572" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfRisksAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfRisksAbstract_019eb852-e030-75f9-801d-d037e314c572" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfContractsIssuedAndOutstanding_019eb852-e030-776f-9432-0661ce38e880" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfContractsIssuedAndOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfRisksAbstract_019eb852-e030-75f9-801d-d037e314c572" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNumberOfContractsIssuedAndOutstanding_019eb852-e030-776f-9432-0661ce38e880" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriodAbstract_019eb852-e030-7302-b256-fb9e737a1270" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriodAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriodAbstract_019eb852-e030-7302-b256-fb9e737a1270" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriod_019eb852-e030-7cbb-bd51-68cd3d45fea5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriodAbstract_019eb852-e030-7302-b256-fb9e737a1270" xlink:to="loc_us-gaap_InsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriod_019eb852-e030-7cbb-bd51-68cd3d45fea5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationRemainingWeightedAverageContractPeriodNet_019eb852-e030-7974-96a7-91a8f52caaee" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationRemainingWeightedAverageContractPeriodNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationRemainingWeightedAverageContractPeriodAbstract_019eb852-e030-7302-b256-fb9e737a1270" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationRemainingWeightedAverageContractPeriodNet_019eb852-e030-7974-96a7-91a8f52caaee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalAbstract_019eb852-e030-7a35-9dec-353a22f14e05" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalAbstract_019eb852-e030-7a35-9dec-353a22f14e05" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal_019eb852-e030-7dcb-83bd-88010997956c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalAbstract_019eb852-e030-7a35-9dec-353a22f14e05" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal_019eb852-e030-7dcb-83bd-88010997956c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalNet_019eb852-e030-7583-8bbb-17238a9f94bb" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalAbstract_019eb852-e030-7a35-9dec-353a22f14e05" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipalNet_019eb852-e030-7583-8bbb-17238a9f94bb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsInterestAbstract_019eb852-e030-77fa-baea-46fff5654426" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsInterestAbstract_019eb852-e030-77fa-baea-46fff5654426" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingInterest_019eb852-e030-710c-aab0-ae7a5a118b25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsInterestAbstract_019eb852-e030-77fa-baea-46fff5654426" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingInterest_019eb852-e030-710c-aab0-ae7a5a118b25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingInterestNet_019eb852-e030-7f75-8e64-d94dd7c7d09f" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingInterestNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsInterestAbstract_019eb852-e030-77fa-baea-46fff5654426" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingInterestNet_019eb852-e030-7f75-8e64-d94dd7c7d09f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingAbstract_019eb852-e030-739c-8398-f9ce6af8ff3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingAbstract_019eb852-e030-739c-8398-f9ce6af8ff3f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstanding_019eb852-e030-7ef2-9b90-d2ff1b30dc83" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingAbstract_019eb852-e030-739c-8398-f9ce6af8ff3f" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstanding_019eb852-e030-7ef2-9b90-d2ff1b30dc83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingNet_019eb852-e030-7ee2-86c3-80065dc9c48b" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingAbstract_019eb852-e030-739c-8398-f9ce6af8ff3f" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingNet_019eb852-e030-7ee2-86c3-80065dc9c48b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationExpectedCashFlowsAbstract_019eb852-e030-70d8-819a-2c838f845ad1" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationExpectedCashFlowsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationExpectedCashFlowsAbstract_019eb852-e030-70d8-819a-2c838f845ad1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiability_019eb852-e030-7e2a-95dd-be11109dac1c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationExpectedCashFlowsAbstract_019eb852-e030-70d8-819a-2c838f845ad1" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiability_019eb852-e030-7e2a-95dd-be11109dac1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilityNetOfReinsurance_019eb852-e030-7291-bf3c-b54d593e6997" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilityNetOfReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationExpectedCashFlowsAbstract_019eb852-e030-70d8-819a-2c838f845ad1" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilityNetOfReinsurance_019eb852-e030-7291-bf3c-b54d593e6997" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveriesAbstract_019eb852-e030-7f34-bfec-fc0ee8168940" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveriesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveriesAbstract_019eb852-e030-7f34-bfec-fc0ee8168940" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveries_019eb852-e030-7375-8c45-d0a16ffe6cb5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveriesAbstract_019eb852-e030-7f34-bfec-fc0ee8168940" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveries_019eb852-e030-7375-8c45-d0a16ffe6cb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationReductionsofGrossClaimLiabilityNetPotentialRecoveries_019eb852-e030-7f27-8a17-f5c39edb6671" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationReductionsofGrossClaimLiabilityNetPotentialRecoveries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityGrossPotentialRecoveriesAbstract_019eb852-e030-7f34-bfec-fc0ee8168940" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationReductionsofGrossClaimLiabilityNetPotentialRecoveries_019eb852-e030-7f27-8a17-f5c39edb6671" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilitySubtotalAbstract_019eb852-e030-7a4f-b178-3539ab58330c" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilitySubtotalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilitySubtotalAbstract_019eb852-e030-7a4f-b178-3539ab58330c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityUndiscountedDirectAssumed_019eb852-e030-747a-80ac-586fd1abea6a" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityUndiscountedDirectAssumed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilitySubtotalAbstract_019eb852-e030-7a4f-b178-3539ab58330c" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityUndiscountedDirectAssumed_019eb852-e030-747a-80ac-586fd1abea6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityUndiscountedDirectAssumedNet_019eb852-e030-736b-886a-98684bb6c783" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityUndiscountedDirectAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationGrossClaimLiabilitySubtotalAbstract_019eb852-e030-7a4f-b178-3539ab58330c" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityUndiscountedDirectAssumedNet_019eb852-e030-736b-886a-98684bb6c783" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscountAbstract_019eb852-e030-7c92-9253-89b1d0acbf27" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscountAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscountAbstract_019eb852-e030-7c92-9253-89b1d0acbf27" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscount_019eb852-e030-7aec-bb65-37a6a9a58a98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscountAbstract_019eb852-e030-7c92-9253-89b1d0acbf27" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscount_019eb852-e030-7aec-bb65-37a6a9a58a98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetOfReinsuranceRecoverableDiscountAccretion_019eb852-e030-73bb-86b4-1d6a22948f7a" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetOfReinsuranceRecoverableDiscountAccretion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetDiscountAbstract_019eb852-e030-7c92-9253-89b1d0acbf27" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityNetOfReinsuranceRecoverableDiscountAccretion_019eb852-e030-73bb-86b4-1d6a22948f7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiabilityAbstract_019eb852-e030-72b1-9a6e-bc2237d9136a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiabilityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiabilityAbstract_019eb852-e030-72b1-9a6e-bc2237d9136a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiability_019eb852-e030-777f-b92b-abef40fd921f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiabilityAbstract_019eb852-e030-72b1-9a6e-bc2237d9136a" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiability_019eb852-e030-777f-b92b-abef40fd921f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityNetofReinsuranceRecoverable_019eb852-e030-79d2-b496-70994a883ba2" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityNetofReinsuranceRecoverable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationNetClaimLiabilityAbstract_019eb852-e030-72b1-9a6e-bc2237d9136a" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationNetClaimLiabilityNetofReinsuranceRecoverable_019eb852-e030-79d2-b496-70994a883ba2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenueAbstract_019eb852-e030-78dd-a297-74d1e76be197" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenueAbstract_019eb852-e030-78dd-a297-74d1e76be197" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenue_019eb852-e030-7c61-ab92-cf229976527a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenueAbstract_019eb852-e030-78dd-a297-74d1e76be197" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenue_019eb852-e030-7c61-ab92-cf229976527a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationStatementofFinancialPositionUnearnedPremiumRevenueNetofReinsuranceRecoverable_019eb852-e030-7d2a-bb4a-28e01eb1f0f8" xlink:href="ago-20260630.xsd#ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationStatementofFinancialPositionUnearnedPremiumRevenueNetofReinsuranceRecoverable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionUnearnedPremiumRevenueAbstract_019eb852-e030-78dd-a297-74d1e76be197" xlink:to="loc_ago_ScheduleofInsuredFinancialObligationswithCreditDeteriorationStatementofFinancialPositionUnearnedPremiumRevenueNetofReinsuranceRecoverable_019eb852-e030-7d2a-bb4a-28e01eb1f0f8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReservesSalvageAbstract_019eb852-e030-7264-93a5-043dbc9d4c5b" xlink:href="ago-20260630.xsd#ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReservesSalvageAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityAbstract_019eb852-e030-75b4-b591-6c18abd35591" xlink:to="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReservesSalvageAbstract_019eb852-e030-7264-93a5-043dbc9d4c5b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionClaimLiability_019eb852-e030-732d-bd8f-14cb2d092ab2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionClaimLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReservesSalvageAbstract_019eb852-e030-7264-93a5-043dbc9d4c5b" xlink:to="loc_us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationStatementOfFinancialPositionClaimLiability_019eb852-e030-732d-bd8f-14cb2d092ab2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseNetofReinsuranceandSalvageSubrogationandOtherRecoveries_019eb852-e030-7f33-a894-11cb011055da" xlink:href="ago-20260630.xsd#ago_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseNetofReinsuranceandSalvageSubrogationandOtherRecoveries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReservesSalvageAbstract_019eb852-e030-7264-93a5-043dbc9d4c5b" xlink:to="loc_ago_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseNetofReinsuranceandSalvageSubrogationandOtherRecoveries_019eb852-e030-7f33-a894-11cb011055da" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/AnnuityReinsuranceAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#AnnuityReinsuranceAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/AnnuityReinsuranceAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-7949-b0b3-2cc033729513" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectsOfReinsuranceLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectsOfReinsuranceTable_019eb852-e030-70dc-8a88-150e455414fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectsOfReinsuranceTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-7949-b0b3-2cc033729513" xlink:to="loc_us-gaap_EffectsOfReinsuranceTable_019eb852-e030-70dc-8a88-150e455414fc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-742e-b12c-3aebf0a25130" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EffectsOfReinsuranceTable_019eb852-e030-70dc-8a88-150e455414fc" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-742e-b12c-3aebf0a25130" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-742e-b12c-3aebf0a25130_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-742e-b12c-3aebf0a25130" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-742e-b12c-3aebf0a25130_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7a06-9f56-a128dc6c5af1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-742e-b12c-3aebf0a25130" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7a06-9f56-a128dc6c5af1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AnnuityReinsuranceMember_019eb852-e030-71c0-881c-495db102e7d6" xlink:href="ago-20260630.xsd#ago_AnnuityReinsuranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7a06-9f56-a128dc6c5af1" xlink:to="loc_ago_AnnuityReinsuranceMember_019eb852-e030-71c0-881c-495db102e7d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AnnuityReinsuranceAgreementNumberOfContracts_019eb852-e030-7a89-aab4-c45d86abc255" xlink:href="ago-20260630.xsd#ago_AnnuityReinsuranceAgreementNumberOfContracts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-7949-b0b3-2cc033729513" xlink:to="loc_ago_AnnuityReinsuranceAgreementNumberOfContracts_019eb852-e030-7a89-aab4-c45d86abc255" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense_019eb852-e030-70d0-bca0-62b474dc767b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-7949-b0b3-2cc033729513" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense_019eb852-e030-70d0-bca0-62b474dc767b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/AnnuityReinsuranceFuturePolicyBenefitsforAnnuityReinsuranceContractsDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#AnnuityReinsuranceFuturePolicyBenefitsforAnnuityReinsuranceContractsDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/AnnuityReinsuranceFuturePolicyBenefitsforAnnuityReinsuranceContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-71ba-bb05-cb886e8f9c97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectsOfReinsuranceLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectsOfReinsuranceTable_019eb852-e030-7451-b564-1fb3d6c1dc59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectsOfReinsuranceTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-71ba-bb05-cb886e8f9c97" xlink:to="loc_us-gaap_EffectsOfReinsuranceTable_019eb852-e030-7451-b564-1fb3d6c1dc59" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-71c2-a8de-0d043d270b3b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EffectsOfReinsuranceTable_019eb852-e030-7451-b564-1fb3d6c1dc59" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-71c2-a8de-0d043d270b3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-71c2-a8de-0d043d270b3b_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-71c2-a8de-0d043d270b3b" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-71c2-a8de-0d043d270b3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7f47-8384-3320fdcad710" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-71c2-a8de-0d043d270b3b" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7f47-8384-3320fdcad710" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AnnuityReinsuranceMember_019eb852-e030-7c44-8d6a-f21bd6e4a0bf" xlink:href="ago-20260630.xsd#ago_AnnuityReinsuranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7f47-8384-3320fdcad710" xlink:to="loc_ago_AnnuityReinsuranceMember_019eb852-e030-7c44-8d6a-f21bd6e4a0bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeferredProfitLiabilityMember_019eb852-e030-7c57-8d2a-643798d6630a" xlink:href="ago-20260630.xsd#ago_DeferredProfitLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7f47-8384-3320fdcad710" xlink:to="loc_ago_DeferredProfitLiabilityMember_019eb852-e030-7c57-8d2a-643798d6630a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitAfterReinsurance_019eb852-e030-7361-8ce1-561a6abeb91e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitAfterReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_019eb852-e030-71ba-bb05-cb886e8f9c97" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitAfterReinsurance_019eb852-e030-7361-8ce1-561a6abeb91e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/AnnuityReinsuranceRollforwardofLiabilityforFuturePolicyBenefitDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#AnnuityReinsuranceRollforwardofLiabilityforFuturePolicyBenefitDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/AnnuityReinsuranceRollforwardofLiabilityforFuturePolicyBenefitDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityTable_019eb852-e030-7366-8b98-55fde330f895" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitActivityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityTable_019eb852-e030-7366-8b98-55fde330f895" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019eb852-e030-78e4-85cf-e65cdf18d4cc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityTable_019eb852-e030-7366-8b98-55fde330f895" xlink:to="loc_srt_ProductOrServiceAxis_019eb852-e030-78e4-85cf-e65cdf18d4cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-78e4-85cf-e65cdf18d4cc_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-78e4-85cf-e65cdf18d4cc" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-78e4-85cf-e65cdf18d4cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019eb852-e030-7eb7-86b8-21d5b0955e07" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019eb852-e030-78e4-85cf-e65cdf18d4cc" xlink:to="loc_srt_ProductsAndServicesDomain_019eb852-e030-7eb7-86b8-21d5b0955e07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AnnuityReinsuranceMember_019eb852-e030-730c-88f5-7ddc1b0ea9fd" xlink:href="ago-20260630.xsd#ago_AnnuityReinsuranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019eb852-e030-7eb7-86b8-21d5b0955e07" xlink:to="loc_ago_AnnuityReinsuranceMember_019eb852-e030-730c-88f5-7ddc1b0ea9fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitOriginalDiscountRateBeforeCashFlowAndReinsurance_019eb852-e030-7efe-b572-d9ed718b6ea1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitOriginalDiscountRateBeforeCashFlowAndReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitOriginalDiscountRateBeforeCashFlowAndReinsurance_019eb852-e030-7efe-b572-d9ed718b6ea1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseFromCashFlowChange_019eb852-e030-798e-8500-5c8ecbe256ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseFromCashFlowChange"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseFromCashFlowChange_019eb852-e030-798e-8500-5c8ecbe256ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseOfActualVarianceFromExpectedExperience_019eb852-e030-7dd0-bb79-913a868ac07f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseOfActualVarianceFromExpectedExperience"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseOfActualVarianceFromExpectedExperience_019eb852-e030-7dd0-bb79-913a868ac07f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFutureBenefitOriginalDiscountRateBeforeReinsuranceAfterCashFlowChange_019eb852-e030-7a42-a5f4-bef9d339de2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFutureBenefitOriginalDiscountRateBeforeReinsuranceAfterCashFlowChange"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFutureBenefitOriginalDiscountRateBeforeReinsuranceAfterCashFlowChange_019eb852-e030-7a42-a5f4-bef9d339de2e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense_019eb852-e030-7d32-8725-63304a2c24a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense_019eb852-e030-7d32-8725-63304a2c24a7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitsPaymentForBenefits_019eb852-e030-77a0-b71b-6f50d175c6bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitsPaymentForBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitsPaymentForBenefits_019eb852-e030-77a0-b71b-6f50d175c6bb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityForFuturePolicyBenefitForeignExchangeRemeasurement_019eb852-e030-7880-a05c-ce413fa21d92" xlink:href="ago-20260630.xsd#ago_LiabilityForFuturePolicyBenefitForeignExchangeRemeasurement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_ago_LiabilityForFuturePolicyBenefitForeignExchangeRemeasurement_019eb852-e030-7880-a05c-ce413fa21d92" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociLiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitBeforeTax_019eb852-e030-7fa8-966b-e0b7112f9153" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociLiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_AociLiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitBeforeTax_019eb852-e030-7fa8-966b-e0b7112f9153" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitAfterReinsurance_019eb852-e030-7827-9bef-54318bc4fb9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitAfterReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitRollForward_019eb852-e030-7cb8-bddd-ec494d397d55" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitAfterReinsurance_019eb852-e030-7827-9bef-54318bc4fb9c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitWeightedAverageDuration_019eb852-e030-7d18-9dd1-5162978d458d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitWeightedAverageDuration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitWeightedAverageDuration_019eb852-e030-7d18-9dd1-5162978d458d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityForFuturePolicyBenefitOriginalWeightedAverageDiscountRate_019eb852-e030-74a7-ad2d-24eedf29b771" xlink:href="ago-20260630.xsd#ago_LiabilityForFuturePolicyBenefitOriginalWeightedAverageDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_ago_LiabilityForFuturePolicyBenefitOriginalWeightedAverageDiscountRate_019eb852-e030-74a7-ad2d-24eedf29b771" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitCurrentWeightedAverageDiscountRate_019eb852-e030-79fc-a063-cd827c6200a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitCurrentWeightedAverageDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitCurrentWeightedAverageDiscountRate_019eb852-e030-79fc-a063-cd827c6200a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitUndiscountedBeforeReinsurance_019eb852-e030-71da-bd33-2382598320e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitUndiscountedBeforeReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitUndiscountedBeforeReinsurance_019eb852-e030-71da-bd33-2382598320e5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitDiscountedBeforeReinsurance_019eb852-e030-7bbf-825c-3be83f51fd7d" xlink:href="ago-20260630.xsd#ago_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitDiscountedBeforeReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_019eb852-e030-7e74-9bab-66b19b2c4e6f" xlink:to="loc_ago_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitDiscountedBeforeReinsurance_019eb852-e030-7bbf-825c-3be83f51fd7d" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/AnnuityReinsuranceRangeofGuaranteedMinimumCreditRatingDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#AnnuityReinsuranceRangeofGuaranteedMinimumCreditRatingDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/AnnuityReinsuranceRangeofGuaranteedMinimumCreditRatingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateLineItems_019eb852-e030-7212-b878-a66b5548cbd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateTable_019eb852-e030-76a5-a946-7c52688a8e6a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateLineItems_019eb852-e030-7212-b878-a66b5548cbd6" xlink:to="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateTable_019eb852-e030-76a5-a946-7c52688a8e6a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeAxis_019eb852-e030-71f4-9aee-2480129762ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateTable_019eb852-e030-76a5-a946-7c52688a8e6a" xlink:to="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeAxis_019eb852-e030-71f4-9aee-2480129762ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain_019eb852-e030-71f4-9aee-2480129762ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeAxis_019eb852-e030-71f4-9aee-2480129762ed" xlink:to="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain_019eb852-e030-71f4-9aee-2480129762ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain_019eb852-e030-70cc-a273-0cf37e233fab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeAxis_019eb852-e030-71f4-9aee-2480129762ed" xlink:to="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain_019eb852-e030-70cc-a273-0cf37e233fab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeFrom0400To0499Member_019eb852-e030-7066-96a4-5b626c70ed4a" xlink:href="ago-20260630.xsd#ago_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeFrom0400To0499Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain_019eb852-e030-70cc-a273-0cf37e233fab" xlink:to="loc_ago_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeFrom0400To0499Member_019eb852-e030-7066-96a4-5b626c70ed4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeFrom0500To0599Member_019eb852-e030-723a-9bfa-c14cb059466c" xlink:href="ago-20260630.xsd#ago_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeFrom0500To0599Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeDomain_019eb852-e030-70cc-a273-0cf37e233fab" xlink:to="loc_ago_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateRangeFrom0500To0599Member_019eb852-e030-723a-9bfa-c14cb059466c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateAxis_019eb852-e030-7393-a8e6-39b39f3e89ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateTable_019eb852-e030-76a5-a946-7c52688a8e6a" xlink:to="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateAxis_019eb852-e030-7393-a8e6-39b39f3e89ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain_019eb852-e030-7393-a8e6-39b39f3e89ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateAxis_019eb852-e030-7393-a8e6-39b39f3e89ff" xlink:to="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain_019eb852-e030-7393-a8e6-39b39f3e89ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain_019eb852-e030-79c0-a3cc-f57082075b30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateAxis_019eb852-e030-7393-a8e6-39b39f3e89ff" xlink:to="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain_019eb852-e030-79c0-a3cc-f57082075b30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceAtGuaranteedMinimumCreditingRateMember_019eb852-e030-798c-bb2e-406dbc60c25b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceAtGuaranteedMinimumCreditingRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PolicyholderAccountBalanceAboveGuaranteedMinimumCreditingRateDomain_019eb852-e030-79c0-a3cc-f57082075b30" xlink:to="loc_us-gaap_PolicyholderAccountBalanceAtGuaranteedMinimumCreditingRateMember_019eb852-e030-798c-bb2e-406dbc60c25b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb852-e030-7b7a-8bbb-4c40406b7f62" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateTable_019eb852-e030-76a5-a946-7c52688a8e6a" xlink:to="loc_srt_RangeAxis_019eb852-e030-7b7a-8bbb-4c40406b7f62" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e030-7b7a-8bbb-4c40406b7f62_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb852-e030-7b7a-8bbb-4c40406b7f62" xlink:to="loc_srt_RangeMember_019eb852-e030-7b7a-8bbb-4c40406b7f62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e030-7c95-89dc-3ffae16cfa10" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb852-e030-7b7a-8bbb-4c40406b7f62" xlink:to="loc_srt_RangeMember_019eb852-e030-7c95-89dc-3ffae16cfa10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb852-e030-784f-89ea-7d5b4485756c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e030-7c95-89dc-3ffae16cfa10" xlink:to="loc_srt_MinimumMember_019eb852-e030-784f-89ea-7d5b4485756c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb852-e030-7ff3-b286-5c3c3baf080a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e030-7c95-89dc-3ffae16cfa10" xlink:to="loc_srt_MaximumMember_019eb852-e030-7ff3-b286-5c3c3baf080a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditRating_019eb852-e030-7117-88d4-8f2a1489abc4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditRating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateLineItems_019eb852-e030-7212-b878-a66b5548cbd6" xlink:to="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditRating_019eb852-e030-7117-88d4-8f2a1489abc4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderFunds_019eb852-e030-758f-9958-6e3092fc06e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderFunds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PolicyholderAccountBalanceGuaranteedMinimumCreditingRateLineItems_019eb852-e030-7212-b878-a66b5548cbd6" xlink:to="loc_us-gaap_PolicyholderFunds_019eb852-e030-758f-9958-6e3092fc06e9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/DerivativesCreditDerivativesSubordinationandRatingsDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#DerivativesCreditDerivativesSubordinationandRatingsDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/DerivativesCreditDerivativesSubordinationandRatingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7cb6-b46c-787d5a86b8b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-76dd-84df-b81600bee141" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfCreditDerivativesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7cb6-b46c-787d5a86b8b5" xlink:to="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-76dd-84df-b81600bee141" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-76af-8bb7-60a53c401c02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-76dd-84df-b81600bee141" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-76af-8bb7-60a53c401c02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-76af-8bb7-60a53c401c02_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-76af-8bb7-60a53c401c02" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-76af-8bb7-60a53c401c02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7100-825d-c3630a150a35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e030-76af-8bb7-60a53c401c02" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7100-825d-c3630a150a35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PublicFinanceMember_019eb852-e030-76b4-9864-24bbe54cc6a1" xlink:href="ago-20260630.xsd#ago_PublicFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7100-825d-c3630a150a35" xlink:to="loc_ago_PublicFinanceMember_019eb852-e030-76b4-9864-24bbe54cc6a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StructuredFinanceMember_019eb852-e030-72f1-800a-5a81df4f4343" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StructuredFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e030-7100-825d-c3630a150a35" xlink:to="loc_us-gaap_StructuredFinanceMember_019eb852-e030-72f1-800a-5a81df4f4343" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e030-751b-ae8c-dd06d640e4b4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-76dd-84df-b81600bee141" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e030-751b-ae8c-dd06d640e4b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e030-751b-ae8c-dd06d640e4b4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e030-751b-ae8c-dd06d640e4b4" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e030-751b-ae8c-dd06d640e4b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e030-7f8a-ad1e-868d37322d9b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e030-751b-ae8c-dd06d640e4b4" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e030-7f8a-ad1e-868d37322d9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e030-7267-8375-56228f4d0e99" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e030-7f8a-ad1e-868d37322d9b" xlink:to="loc_country_US_019eb852-e030-7267-8375-56228f4d0e99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019eb852-e030-7339-80da-45ff280270af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e030-7f8a-ad1e-868d37322d9b" xlink:to="loc_us-gaap_NonUsMember_019eb852-e030-7339-80da-45ff280270af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AverageTermOfCreditRiskDerivatives1_019eb852-e030-7599-927e-bc075a6e777a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AverageTermOfCreditRiskDerivatives1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7cb6-b46c-787d5a86b8b5" xlink:to="loc_us-gaap_AverageTermOfCreditRiskDerivatives1_019eb852-e030-7599-927e-bc075a6e777a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesAbstract_019eb852-e030-7b99-8bc9-680896129e71" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7cb6-b46c-787d5a86b8b5" xlink:to="loc_ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesAbstract_019eb852-e030-7b99-8bc9-680896129e71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyContractsAccountedforasCreditDerivativesOutstandingPrincipalAmount_019eb852-e030-7a50-99de-9b09c69db099" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyContractsAccountedforasCreditDerivativesOutstandingPrincipalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesAbstract_019eb852-e030-7b99-8bc9-680896129e71" xlink:to="loc_ago_FinancialGuarantyContractsAccountedforasCreditDerivativesOutstandingPrincipalAmount_019eb852-e030-7a50-99de-9b09c69db099" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditRiskDerivativesAtFairValueNet_019eb852-e030-76ff-9a37-bad61bb3f077" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditRiskDerivativesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_FinancialGuarantyContractsAccountedForAsCreditDerivativesAbstract_019eb852-e030-7b99-8bc9-680896129e71" xlink:to="loc_us-gaap_CreditRiskDerivativesAtFairValueNet_019eb852-e030-76ff-9a37-bad61bb3f077" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/DerivativesCDSSpreadandComponentsofCreditDerivativeAssetsLiabilitiesDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#DerivativesCDSSpreadandComponentsofCreditDerivativeAssetsLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/DerivativesCDSSpreadandComponentsofCreditDerivativeAssetsLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-70fb-915a-aa979441fdf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-78e9-9a72-f0975c4e5ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfCreditDerivativesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-70fb-915a-aa979441fdf0" xlink:to="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-78e9-9a72-f0975c4e5ad2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7f0f-8f9a-04bcb77f4888" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-78e9-9a72-f0975c4e5ad2" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7f0f-8f9a-04bcb77f4888" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7f0f-8f9a-04bcb77f4888_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7f0f-8f9a-04bcb77f4888" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7f0f-8f9a-04bcb77f4888_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7427-a56c-a67bea113265" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7f0f-8f9a-04bcb77f4888" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7427-a56c-a67bea113265" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CreditRiskContract5YearSpreadMember_019eb852-e030-71a6-ae42-6f755dfb1f14" xlink:href="ago-20260630.xsd#ago_CreditRiskContract5YearSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7427-a56c-a67bea113265" xlink:to="loc_ago_CreditRiskContract5YearSpreadMember_019eb852-e030-71a6-ae42-6f755dfb1f14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CreditRiskContract1YearSpreadMember_019eb852-e030-7744-a18f-9c50b949d4be" xlink:href="ago-20260630.xsd#ago_CreditRiskContract1YearSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7427-a56c-a67bea113265" xlink:to="loc_ago_CreditRiskContract1YearSpreadMember_019eb852-e030-7744-a18f-9c50b949d4be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019eb852-e030-7fa0-bd2a-dcb61838fae9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-78e9-9a72-f0975c4e5ad2" xlink:to="loc_dei_LegalEntityAxis_019eb852-e030-7fa0-bd2a-dcb61838fae9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e030-7fa0-bd2a-dcb61838fae9_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019eb852-e030-7fa0-bd2a-dcb61838fae9" xlink:to="loc_dei_EntityDomain_019eb852-e030-7fa0-bd2a-dcb61838fae9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e030-72ba-8f33-e781037deeff" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019eb852-e030-7fa0-bd2a-dcb61838fae9" xlink:to="loc_dei_EntityDomain_019eb852-e030-72ba-8f33-e781037deeff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyIncMember_019eb852-e030-7318-bffd-6441a3091128" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019eb852-e030-72ba-8f33-e781037deeff" xlink:to="loc_ago_AssuredGuarantyIncMember_019eb852-e030-7318-bffd-6441a3091128" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CreditDerivativeQuotedPrice_019eb852-e030-7bb2-bd18-6be8588121fd" xlink:href="ago-20260630.xsd#ago_CreditDerivativeQuotedPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-70fb-915a-aa979441fdf0" xlink:to="loc_ago_CreditDerivativeQuotedPrice_019eb852-e030-7bb2-bd18-6be8588121fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CreditRiskDerivativesAtFairValueBeforeEffectOfCreditSpreadNet_019eb852-e030-76be-98bc-a0e0a558a9d7" xlink:href="ago-20260630.xsd#ago_CreditRiskDerivativesAtFairValueBeforeEffectOfCreditSpreadNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-70fb-915a-aa979441fdf0" xlink:to="loc_ago_CreditRiskDerivativesAtFairValueBeforeEffectOfCreditSpreadNet_019eb852-e030-76be-98bc-a0e0a558a9d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCreditRiskValuationAdjustmentDerivativeLiabilities_019eb852-e030-7b65-abe1-3e9f00d8d012" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeCreditRiskValuationAdjustmentDerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-70fb-915a-aa979441fdf0" xlink:to="loc_us-gaap_DerivativeCreditRiskValuationAdjustmentDerivativeLiabilities_019eb852-e030-7b65-abe1-3e9f00d8d012" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditRiskDerivativesAtFairValueNet_019eb852-e030-7a42-b3cd-b7249057d141" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditRiskDerivativesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-70fb-915a-aa979441fdf0" xlink:to="loc_us-gaap_CreditRiskDerivativesAtFairValueNet_019eb852-e030-7a42-b3cd-b7249057d141" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/DerivativesNoncreditDerivativesDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#DerivativesNoncreditDerivativesDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/DerivativesNoncreditDerivativesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7410-bbce-14e299d36f60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7203-bdf3-78a2e3c4254d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfCreditDerivativesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7410-bbce-14e299d36f60" xlink:to="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7203-bdf3-78a2e3c4254d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7267-9198-c09d3faae962" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7203-bdf3-78a2e3c4254d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7267-9198-c09d3faae962" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7267-9198-c09d3faae962_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7267-9198-c09d3faae962" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7267-9198-c09d3faae962_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7950-a09d-9487d7531adb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7267-9198-c09d3faae962" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7950-a09d-9487d7531adb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrencySwapMember_019eb852-e030-7498-b9bf-8a5b7cc92ced" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CurrencySwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7950-a09d-9487d7531adb" xlink:to="loc_us-gaap_CurrencySwapMember_019eb852-e030-7498-b9bf-8a5b7cc92ced" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019eb852-e030-7ca3-b230-f7f360c5aeee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7950-a09d-9487d7531adb" xlink:to="loc_us-gaap_InterestRateSwapMember_019eb852-e030-7ca3-b230-f7f360c5aeee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InflationSwapMember_019eb852-e030-78d8-8b03-28cb2aa0882b" xlink:href="ago-20260630.xsd#ago_InflationSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7950-a09d-9487d7531adb" xlink:to="loc_ago_InflationSwapMember_019eb852-e030-78d8-8b03-28cb2aa0882b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019eb852-e030-7da9-9cfb-c877f9f2aedc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7410-bbce-14e299d36f60" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019eb852-e030-7da9-9cfb-c877f9f2aedc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019eb852-e030-7514-9c6d-74630df99d09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7410-bbce-14e299d36f60" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019eb852-e030-7514-9c6d-74630df99d09" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/DerivativesNetChangeinFairValueofCreditDerivativesGainsLossesDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#DerivativesNetChangeinFairValueofCreditDerivativesGainsLossesDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/DerivativesNetChangeinFairValueofCreditDerivativesGainsLossesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7f70-aeb8-8df242185472" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7652-a8be-a0152cfa84ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfCreditDerivativesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7f70-aeb8-8df242185472" xlink:to="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7652-a8be-a0152cfa84ad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7d6e-9451-b3921565caa0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7652-a8be-a0152cfa84ad" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7d6e-9451-b3921565caa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7d6e-9451-b3921565caa0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7d6e-9451-b3921565caa0" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7d6e-9451-b3921565caa0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7ee1-a850-8e442dae6d0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e030-7d6e-9451-b3921565caa0" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7ee1-a850-8e442dae6d0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrencySwapMember_019eb852-e030-7656-a698-c80026b3448d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CurrencySwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7ee1-a850-8e442dae6d0e" xlink:to="loc_us-gaap_CurrencySwapMember_019eb852-e030-7656-a698-c80026b3448d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019eb852-e030-7360-b184-29906e3f04aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7ee1-a850-8e442dae6d0e" xlink:to="loc_us-gaap_InterestRateSwapMember_019eb852-e030-7360-b184-29906e3f04aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InflationSwapMember_019eb852-e030-71e6-9a9a-366d662160e3" xlink:href="ago-20260630.xsd#ago_InflationSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7ee1-a850-8e442dae6d0e" xlink:to="loc_ago_InflationSwapMember_019eb852-e030-71e6-9a9a-366d662160e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_019eb852-e030-78e6-8502-8d05cfa64eda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e030-7ee1-a850-8e442dae6d0e" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_019eb852-e030-78e6-8502-8d05cfa64eda" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeAxis_019eb852-e030-72f1-a070-717d391628bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingActivityByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-7652-a8be-a0152cfa84ad" xlink:to="loc_us-gaap_TradingActivityByTypeAxis_019eb852-e030-72f1-a070-717d391628bb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019eb852-e030-72f1-a070-717d391628bb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019eb852-e030-72f1-a070-717d391628bb" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019eb852-e030-72f1-a070-717d391628bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019eb852-e030-7536-8e66-7611b50279be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019eb852-e030-72f1-a070-717d391628bb" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019eb852-e030-7536-8e66-7611b50279be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditMember_019eb852-e030-7eba-84bd-cd6f535d98da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityByTypeDomain_019eb852-e030-7536-8e66-7611b50279be" xlink:to="loc_us-gaap_CreditMember_019eb852-e030-7eba-84bd-cd6f535d98da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CreditDerivativeRealizedGainLossandOtherSettlements_019eb852-e030-764a-aa8a-e27a9fc34562" xlink:href="ago-20260630.xsd#ago_CreditDerivativeRealizedGainLossandOtherSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7f70-aeb8-8df242185472" xlink:to="loc_ago_CreditDerivativeRealizedGainLossandOtherSettlements_019eb852-e030-764a-aa8a-e27a9fc34562" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019eb852-e030-7259-86f0-c276f1f5d78c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7f70-aeb8-8df242185472" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_019eb852-e030-7259-86f0-c276f1f5d78c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019eb852-e030-71b3-9fd8-d67aa0d6f6e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7f70-aeb8-8df242185472" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019eb852-e030-71b3-9fd8-d67aa0d6f6e0" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/DerivativesNarrativeDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#DerivativesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/DerivativesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7605-b668-638b8c14d257" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-75a8-817c-7c939df5cbc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfCreditDerivativesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7605-b668-638b8c14d257" xlink:to="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-75a8-817c-7c939df5cbc8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019eb852-e030-76f2-9986-d089a42e9192" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-75a8-817c-7c939df5cbc8" xlink:to="loc_srt_LitigationCaseAxis_019eb852-e030-76f2-9986-d089a42e9192" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019eb852-e030-76f2-9986-d089a42e9192_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019eb852-e030-76f2-9986-d089a42e9192" xlink:to="loc_srt_LitigationCaseTypeDomain_019eb852-e030-76f2-9986-d089a42e9192_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019eb852-e030-7f27-9d92-868d6edb102c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019eb852-e030-76f2-9986-d089a42e9192" xlink:to="loc_srt_LitigationCaseTypeDomain_019eb852-e030-7f27-9d92-868d6edb102c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LehmanBrothersInternationalEuropeVsAgFinancialProductsIncMember_019eb852-e030-7488-b762-dd17e698416d" xlink:href="ago-20260630.xsd#ago_LehmanBrothersInternationalEuropeVsAgFinancialProductsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019eb852-e030-7f27-9d92-868d6edb102c" xlink:to="loc_ago_LehmanBrothersInternationalEuropeVsAgFinancialProductsIncMember_019eb852-e030-7488-b762-dd17e698416d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainContingenciesByNatureAxis_019eb852-e030-7bdf-b38f-6f7ee86df8d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainContingenciesByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-75a8-817c-7c939df5cbc8" xlink:to="loc_us-gaap_GainContingenciesByNatureAxis_019eb852-e030-7bdf-b38f-6f7ee86df8d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainContingencyNatureDomain_019eb852-e030-7bdf-b38f-6f7ee86df8d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GainContingenciesByNatureAxis_019eb852-e030-7bdf-b38f-6f7ee86df8d4" xlink:to="loc_us-gaap_GainContingencyNatureDomain_019eb852-e030-7bdf-b38f-6f7ee86df8d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainContingencyNatureDomain_019eb852-e030-76be-9a84-6abba3a72f08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GainContingenciesByNatureAxis_019eb852-e030-7bdf-b38f-6f7ee86df8d4" xlink:to="loc_us-gaap_GainContingencyNatureDomain_019eb852-e030-76be-9a84-6abba3a72f08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositiveOutcomeOfLitigationMember_019eb852-e030-7873-8317-e69d22d86900" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PositiveOutcomeOfLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingencyNatureDomain_019eb852-e030-76be-9a84-6abba3a72f08" xlink:to="loc_us-gaap_PositiveOutcomeOfLitigationMember_019eb852-e030-7873-8317-e69d22d86900" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_019eb852-e030-711a-81ee-a5331117248e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-75a8-817c-7c939df5cbc8" xlink:to="loc_us-gaap_LitigationStatusAxis_019eb852-e030-711a-81ee-a5331117248e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_019eb852-e030-711a-81ee-a5331117248e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_019eb852-e030-711a-81ee-a5331117248e" xlink:to="loc_us-gaap_LitigationStatusDomain_019eb852-e030-711a-81ee-a5331117248e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_019eb852-e030-7e38-80b3-71267d74a444" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_019eb852-e030-711a-81ee-a5331117248e" xlink:to="loc_us-gaap_LitigationStatusDomain_019eb852-e030-7e38-80b3-71267d74a444" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SettledLitigationMember_019eb852-e030-70d4-b80c-4891c913382a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SettledLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_019eb852-e030-7e38-80b3-71267d74a444" xlink:to="loc_us-gaap_SettledLitigationMember_019eb852-e030-70d4-b80c-4891c913382a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019eb852-e030-7b3e-a867-96a4a997c928" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCreditDerivativesTable_019eb852-e030-75a8-817c-7c939df5cbc8" xlink:to="loc_dei_LegalEntityAxis_019eb852-e030-7b3e-a867-96a4a997c928" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e030-7b3e-a867-96a4a997c928_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019eb852-e030-7b3e-a867-96a4a997c928" xlink:to="loc_dei_EntityDomain_019eb852-e030-7b3e-a867-96a4a997c928_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e030-7473-89ff-59c0e1e76f07" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019eb852-e030-7b3e-a867-96a4a997c928" xlink:to="loc_dei_EntityDomain_019eb852-e030-7473-89ff-59c0e1e76f07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyFinancialProductsIncMember_019eb852-e030-77ad-b47a-fdcc2a184ee1" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyFinancialProductsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019eb852-e030-7473-89ff-59c0e1e76f07" xlink:to="loc_ago_AssuredGuarantyFinancialProductsIncMember_019eb852-e030-77ad-b47a-fdcc2a184ee1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementGain_019eb852-e030-7b4e-8770-41cde46ee8c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationSettlementGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesLineItems_019eb852-e030-7605-b668-638b8c14d257" xlink:to="loc_us-gaap_LitigationSettlementGain_019eb852-e030-7b4e-8770-41cde46ee8c7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/InvestmentsAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#InvestmentsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/InvestmentsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_019eb852-e030-7224-b5b8-b403714ad72e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_019eb852-e030-7224-b5b8-b403714ad72e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_019eb852-e030-7224-b5b8-b403714ad72e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_019eb852-e030-7224-b5b8-b403714ad72e" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_019eb852-e030-7224-b5b8-b403714ad72e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_019eb852-e030-7747-ad25-336543a0d4bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_019eb852-e030-7224-b5b8-b403714ad72e" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_019eb852-e030-7747-ad25-336543a0d4bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FutureEquityInvestmentsMember_019eb852-e030-746e-8041-d303ec728ff2" xlink:href="ago-20260630.xsd#ago_FutureEquityInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_019eb852-e030-7747-ad25-336543a0d4bb" xlink:to="loc_ago_FutureEquityInvestmentsMember_019eb852-e030-746e-8041-d303ec728ff2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019eb852-e030-7f1f-9448-36621759a053" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:to="loc_dei_LegalEntityAxis_019eb852-e030-7f1f-9448-36621759a053" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e030-7f1f-9448-36621759a053_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019eb852-e030-7f1f-9448-36621759a053" xlink:to="loc_dei_EntityDomain_019eb852-e030-7f1f-9448-36621759a053_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e030-7945-af28-cd525d3eb605" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019eb852-e030-7f1f-9448-36621759a053" xlink:to="loc_dei_EntityDomain_019eb852-e030-7945-af28-cd525d3eb605" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantySubsidiariesMember_019eb852-e030-700b-abec-f670c8ed4431" xlink:href="ago-20260630.xsd#ago_AssuredGuarantySubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019eb852-e030-7945-af28-cd525d3eb605" xlink:to="loc_ago_AssuredGuarantySubsidiariesMember_019eb852-e030-700b-abec-f670c8ed4431" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e030-7e56-8f6f-ef8a1b339182" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e030-7e56-8f6f-ef8a1b339182" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e030-7e56-8f6f-ef8a1b339182_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e030-7e56-8f6f-ef8a1b339182" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e030-7e56-8f6f-ef8a1b339182_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e030-7ab6-82b9-f90ef6ea8729" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e030-7e56-8f6f-ef8a1b339182" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e030-7ab6-82b9-f90ef6ea8729" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SoundPointCapitalManagementLPMember_019eb852-e030-73eb-ab22-68814e5f4a59" xlink:href="ago-20260630.xsd#ago_SoundPointCapitalManagementLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e030-7ab6-82b9-f90ef6ea8729" xlink:to="loc_ago_SoundPointCapitalManagementLPMember_019eb852-e030-73eb-ab22-68814e5f4a59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e030-7abe-b750-4562093bcfb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e030-7abe-b750-4562093bcfb9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7abe-b750-4562093bcfb9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e030-7abe-b750-4562093bcfb9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7abe-b750-4562093bcfb9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e030-7abe-b750-4562093bcfb9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_CollateralizedLoanObligationEquityTranchesMember_019eb852-e030-7bc4-927d-e3d16048dcce" xlink:href="ago-20260630.xsd#ago_CollateralizedLoanObligationEquityTranchesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:to="loc_ago_CollateralizedLoanObligationEquityTranchesMember_019eb852-e030-7bc4-927d-e3d16048dcce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiquidityBondsMember_019eb852-e030-7c63-9a57-fed5d352701a" xlink:href="ago-20260630.xsd#ago_LiquidityBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:to="loc_ago_LiquidityBondsMember_019eb852-e030-7c63-9a57-fed5d352701a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsLossMitigationSecuritiesMember_019eb852-e030-7ef1-a7ed-609b98ebb8e8" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsLossMitigationSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:to="loc_ago_InsuredFinancialObligationsLossMitigationSecuritiesMember_019eb852-e030-7ef1-a7ed-609b98ebb8e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentOtherMember_019eb852-e030-7870-b158-0bac5249e547" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:to="loc_us-gaap_FinancialInstrumentOtherMember_019eb852-e030-7870-b158-0bac5249e547" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ContingentValueInstrumentsMember_019eb852-e030-7a1a-b97b-073ca0e0df02" xlink:href="ago-20260630.xsd#ago_ContingentValueInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e030-7ac8-826a-91b2a207172f" xlink:to="loc_ago_ContingentValueInstrumentsMember_019eb852-e030-7a1a-b97b-073ca0e0df02" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_019eb852-e030-7b6d-95cc-ff9c81b9a035" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e030-7754-a26b-d45256e082cd" xlink:to="loc_us-gaap_PledgedStatusAxis_019eb852-e030-7b6d-95cc-ff9c81b9a035" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019eb852-e030-7b6d-95cc-ff9c81b9a035_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_019eb852-e030-7b6d-95cc-ff9c81b9a035" xlink:to="loc_us-gaap_PledgedStatusDomain_019eb852-e030-7b6d-95cc-ff9c81b9a035_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019eb852-e030-7431-8537-d148b417b07b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_019eb852-e030-7b6d-95cc-ff9c81b9a035" xlink:to="loc_us-gaap_PledgedStatusDomain_019eb852-e030-7431-8537-d148b417b07b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralMember_019eb852-e030-72dc-8ff3-d285cf1a6696" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetPledgedAsCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_019eb852-e030-7431-8537-d148b417b07b" xlink:to="loc_us-gaap_AssetPledgedAsCollateralMember_019eb852-e030-72dc-8ff3-d285cf1a6696" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InvestmentsAuthorizedAmountToInvest_019eb852-e030-794b-9bfa-5113cb4db8a0" xlink:href="ago-20260630.xsd#ago_InvestmentsAuthorizedAmountToInvest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_ago_InvestmentsAuthorizedAmountToInvest_019eb852-e030-794b-9bfa-5113cb4db8a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FixedMaturityInvestmentsNonInvestmentGradeNotRatedPercent_019eb852-e030-741b-b54e-c37dd31f77ec" xlink:href="ago-20260630.xsd#ago_FixedMaturityInvestmentsNonInvestmentGradeNotRatedPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_ago_FixedMaturityInvestmentsNonInvestmentGradeNotRatedPercent_019eb852-e030-741b-b54e-c37dd31f77ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e030-7a28-9657-6a60c7bb3cbd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e030-7a28-9657-6a60c7bb3cbd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AlternativeInvestment_019eb852-e030-725e-8c64-c76459ec17b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AlternativeInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_AlternativeInvestment_019eb852-e030-725e-8c64-c76459ec17b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_019eb852-e030-7e43-9900-43a076e3bc8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_019eb852-e030-7e43-9900-43a076e3bc8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AlternativeInvestmentsUnfundedCommitment_019eb852-e030-7050-b10c-108cadf29d11" xlink:href="ago-20260630.xsd#ago_AlternativeInvestmentsUnfundedCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_ago_AlternativeInvestmentsUnfundedCommitment_019eb852-e030-7050-b10c-108cadf29d11" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AlternativeInvestmentsAuthorizedAmountToInvest_019eb852-e030-7c11-b7db-4947f0f92b32" xlink:href="ago-20260630.xsd#ago_AlternativeInvestmentsAuthorizedAmountToInvest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_ago_AlternativeInvestmentsAuthorizedAmountToInvest_019eb852-e030-7c11-b7db-4947f0f92b32" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedInvestmentIncomeReceivable_019eb852-e030-7e29-bc6b-0f565a95e53a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccruedInvestmentIncomeReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_AccruedInvestmentIncomeReceivable_019eb852-e030-7e29-bc6b-0f565a95e53a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionGreaterThan10PercentOfBookValueTwelveMonthsOrLongerNumber_019eb852-e030-7012-ad4d-31ce21a24656" xlink:href="ago-20260630.xsd#ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionGreaterThan10PercentOfBookValueTwelveMonthsOrLongerNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionGreaterThan10PercentOfBookValueTwelveMonthsOrLongerNumber_019eb852-e030-7012-ad4d-31ce21a24656" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerGreaterThan10PercentBookValueAggregateLosses_019eb852-e030-7da3-936e-312c716bf035" xlink:href="ago-20260630.xsd#ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerGreaterThan10PercentBookValueAggregateLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerGreaterThan10PercentBookValueAggregateLosses_019eb852-e030-7da3-936e-312c716bf035" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsHeldInTrust_019eb852-e030-7496-9c44-a074c2212733" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsHeldInTrust"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_AssetsHeldInTrust_019eb852-e030-7496-9c44-a074c2212733" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-71e5-ad6d-aa091cd65db7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-71e5-ad6d-aa091cd65db7" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt_019f1a15-fba5-7ca3-b4af-e8b17700ea2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt_019f1a15-fba5-7ca3-b4af-e8b17700ea2a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSalePurchasedWithCreditDeteriorationAmountAtPurchasePrice_019eb852-e0e8-7430-b5f9-0f22bd144baf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSalePurchasedWithCreditDeteriorationAmountAtPurchasePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e030-7d9d-8c6e-ea57b2f1e5e4" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSalePurchasedWithCreditDeteriorationAmountAtPurchasePrice_019eb852-e0e8-7430-b5f9-0f22bd144baf" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/InvestmentsInternallyManagedInvestmentPortfolioDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#InvestmentsInternallyManagedInvestmentPortfolioDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/InvestmentsInternallyManagedInvestmentPortfolioDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7c3a-b79d-7c2d23e4a30b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7c3a-b79d-7c2d23e4a30b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7ff3-9806-897cb9c32cab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7c3a-b79d-7c2d23e4a30b" xlink:to="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7ff3-9806-897cb9c32cab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7ff3-9806-897cb9c32cab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7ff3-9806-897cb9c32cab" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7ff3-9806-897cb9c32cab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7751-90cb-bfedbc63afa7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7ff3-9806-897cb9c32cab" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7751-90cb-bfedbc63afa7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FundsAndOtherInvestmentsMember_019eb852-e0e8-728a-80c9-92d3de0c4014" xlink:href="ago-20260630.xsd#ago_FundsAndOtherInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7751-90cb-bfedbc63afa7" xlink:to="loc_ago_FundsAndOtherInvestmentsMember_019eb852-e0e8-728a-80c9-92d3de0c4014" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e0e8-7696-b5e8-3b83dc43d39e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7c3a-b79d-7c2d23e4a30b" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e0e8-7696-b5e8-3b83dc43d39e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e0e8-7696-b5e8-3b83dc43d39e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e0e8-7696-b5e8-3b83dc43d39e" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e0e8-7696-b5e8-3b83dc43d39e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e0e8-7273-98f8-a51dc7df63fc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019eb852-e0e8-7696-b5e8-3b83dc43d39e" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e0e8-7273-98f8-a51dc7df63fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SoundPointCapitalManagementLPMember_019eb852-e0e8-78b1-8d91-57d2d6ce86b4" xlink:href="ago-20260630.xsd#ago_SoundPointCapitalManagementLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e0e8-7273-98f8-a51dc7df63fc" xlink:to="loc_ago_SoundPointCapitalManagementLPMember_019eb852-e0e8-78b1-8d91-57d2d6ce86b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FundsAndOtherInvestmentsMember_019eb852-e0e8-7bfe-9a34-49fc21f479db" xlink:href="ago-20260630.xsd#ago_FundsAndOtherInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019eb852-e0e8-7273-98f8-a51dc7df63fc" xlink:to="loc_ago_FundsAndOtherInvestmentsMember_019eb852-e0e8-7bfe-9a34-49fc21f479db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7a93-b8d6-5f304613751f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7a93-b8d6-5f304613751f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-7ace-abd3-603e6e93ba64" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-7ace-abd3-603e6e93ba64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermInvestments_019eb852-e0e8-7b13-bcdb-bfb6f367566f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_OtherShortTermInvestments_019eb852-e0e8-7b13-bcdb-bfb6f367566f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019eb852-e0e8-74cd-83cf-1f2368f3b98b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_EquityMethodInvestments_019eb852-e0e8-74cd-83cf-1f2368f3b98b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestments_019eb852-e0e8-712f-82f8-c5dd66052039" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLongTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_OtherLongTermInvestments_019eb852-e0e8-712f-82f8-c5dd66052039" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_019eb852-e0e8-7660-9a5c-4da154a33b19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Investments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_019eb852-e0e8-7bd9-a769-8e56ce0d6157" xlink:to="loc_us-gaap_Investments_019eb852-e0e8-7660-9a5c-4da154a33b19" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/InvestmentsFixedMaturitySecuritiesandShortTermInvestmentsDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#InvestmentsFixedMaturitySecuritiesandShortTermInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/InvestmentsFixedMaturitySecuritiesandShortTermInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-75b0-b2b5-23242890f02f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-75b0-b2b5-23242890f02f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7ede-899c-3c0fa2b69c61" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-75b0-b2b5-23242890f02f" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7ede-899c-3c0fa2b69c61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7ede-899c-3c0fa2b69c61_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7ede-899c-3c0fa2b69c61" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7ede-899c-3c0fa2b69c61_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7ede-899c-3c0fa2b69c61" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-78c7-b9ac-466aade9d5ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-78c7-b9ac-466aade9d5ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019eb852-e0e8-775f-b8e3-71ac29d6c5a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019eb852-e0e8-775f-b8e3-71ac29d6c5a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-7d59-85f9-09ce2c1905e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-7d59-85f9-09ce2c1905e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-71ba-990f-699b1d61cf50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-71ba-990f-699b1d61cf50" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7779-b7e9-35d5e631c570" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7779-b7e9-35d5e631c570" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedLoanObligationsMember_019eb852-e0e8-7aa3-8a64-5d2291b2a4a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CollateralizedLoanObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_CollateralizedLoanObligationsMember_019eb852-e0e8-7aa3-8a64-5d2291b2a4a8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherAssetBackedSecuritiesMember_019eb852-e0e8-7c58-ae10-8e40b6cd698a" xlink:href="ago-20260630.xsd#ago_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_ago_OtherAssetBackedSecuritiesMember_019eb852-e0e8-7c58-ae10-8e40b6cd698a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019eb852-e0e8-77c3-815d-a9aafc783a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7002-8405-1b0ee2d539bd" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019eb852-e0e8-77c3-815d-a9aafc783a4b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019eb852-e0e8-7eba-b4dc-bedd8e3ecc90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-75b0-b2b5-23242890f02f" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019eb852-e0e8-7eba-b4dc-bedd8e3ecc90" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019eb852-e0e8-7eba-b4dc-bedd8e3ecc90_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019eb852-e0e8-7eba-b4dc-bedd8e3ecc90" xlink:to="loc_us-gaap_RelatedPartyDomain_019eb852-e0e8-7eba-b4dc-bedd8e3ecc90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019eb852-e0e8-7a61-869c-3e04c74554e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019eb852-e0e8-7eba-b4dc-bedd8e3ecc90" xlink:to="loc_us-gaap_RelatedPartyDomain_019eb852-e0e8-7a61-869c-3e04c74554e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_019eb852-e0e8-76fc-9e3d-5f06fe9a7d31" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019eb852-e0e8-7a61-869c-3e04c74554e6" xlink:to="loc_srt_AffiliatedEntityMember_019eb852-e0e8-76fc-9e3d-5f06fe9a7d31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PercentageofAvailableforsaleSecuritiesatAmortizedCost_019eb852-e0e8-776a-89c2-50541b554448" xlink:href="ago-20260630.xsd#ago_PercentageofAvailableforsaleSecuritiesatAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_ago_PercentageofAvailableforsaleSecuritiesatAmortizedCost_019eb852-e0e8-776a-89c2-50541b554448" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb852-e0e8-7fbd-af58-5b51bca2b36e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb852-e0e8-7fbd-af58-5b51bca2b36e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest_019eb852-e0e8-7fc0-acf6-a1733c96fe2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest_019eb852-e0e8-7fc0-acf6-a1733c96fe2f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019eb852-e0e8-7fff-a036-e0a603bd7463" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019eb852-e0e8-7fff-a036-e0a603bd7463" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019eb852-e0e8-7964-95a2-4f7c70660e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019eb852-e0e8-7964-95a2-4f7c70660e3e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7161-acef-37ba19314472" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7161-acef-37ba19314472" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_GovernmentAgencyObligationsAsPercentageOfTotalMortgageBackedSecurities_019eb852-e0e8-7028-8256-6dfa10c35528" xlink:href="ago-20260630.xsd#ago_GovernmentAgencyObligationsAsPercentageOfTotalMortgageBackedSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019eb852-e0e8-75d5-a63b-427aa42f3304" xlink:to="loc_ago_GovernmentAgencyObligationsAsPercentageOfTotalMortgageBackedSecurities_019eb852-e0e8-7028-8256-6dfa10c35528" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/InvestmentsGrossUnrealizedLossbyLengthofTimeDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#InvestmentsGrossUnrealizedLossbyLengthofTimeDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/InvestmentsGrossUnrealizedLossbyLengthofTimeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb852-e0e8-790e-b0dd-7b6cb6b30326" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7a7d-ba83-ed272bb576b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb852-e0e8-790e-b0dd-7b6cb6b30326" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7a7d-ba83-ed272bb576b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7c41-9355-7e8975c92503" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7a7d-ba83-ed272bb576b1" xlink:to="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7c41-9355-7e8975c92503" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7c41-9355-7e8975c92503_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7c41-9355-7e8975c92503" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7c41-9355-7e8975c92503_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-7c41-9355-7e8975c92503" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7a2b-b22d-0d3140cb6804" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7a2b-b22d-0d3140cb6804" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019eb852-e0e8-7f57-9b5f-b1c3c1343f00" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019eb852-e0e8-7f57-9b5f-b1c3c1343f00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-73d5-8dc2-b41ceb1c221d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-73d5-8dc2-b41ceb1c221d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7ea5-bef7-3bcdffbd0254" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7ea5-bef7-3bcdffbd0254" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7501-83b8-6ed3d5c4f642" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7501-83b8-6ed3d5c4f642" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedLoanObligationsMember_019eb852-e0e8-7490-82b4-5fb3f300448f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CollateralizedLoanObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_CollateralizedLoanObligationsMember_019eb852-e0e8-7490-82b4-5fb3f300448f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherAssetBackedSecuritiesMember_019eb852-e0e8-71b1-bf6e-996e15ca0bdf" xlink:href="ago-20260630.xsd#ago_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_ago_OtherAssetBackedSecuritiesMember_019eb852-e0e8-71b1-bf6e-996e15ca0bdf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019eb852-e0e8-72ab-a15d-cd7feac3fc5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-7034-8c11-1e8819bf74fd" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019eb852-e0e8-72ab-a15d-cd7feac3fc5c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_DeptSecurityAvailableforsaleSecuritiesContinuousUnrealizedLossPositionAbstract_019eb852-e0e8-7933-bcbe-e716abd3a74d" xlink:href="ago-20260630.xsd#ago_DeptSecurityAvailableforsaleSecuritiesContinuousUnrealizedLossPositionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb852-e0e8-790e-b0dd-7b6cb6b30326" xlink:to="loc_ago_DeptSecurityAvailableforsaleSecuritiesContinuousUnrealizedLossPositionAbstract_019eb852-e0e8-7933-bcbe-e716abd3a74d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAbstract_019eb852-e0e8-7c6d-86d8-d153c4c96d28" xlink:href="ago-20260630.xsd#ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DeptSecurityAvailableforsaleSecuritiesContinuousUnrealizedLossPositionAbstract_019eb852-e0e8-7933-bcbe-e716abd3a74d" xlink:to="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAbstract_019eb852-e0e8-7c6d-86d8-d153c4c96d28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019eb852-e0e8-76b0-8dde-9a5490c48cc3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAbstract_019eb852-e0e8-7c6d-86d8-d153c4c96d28" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019eb852-e0e8-76b0-8dde-9a5490c48cc3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019eb852-e0e8-71b7-ba46-fb7b10354d91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAbstract_019eb852-e0e8-7c6d-86d8-d153c4c96d28" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019eb852-e0e8-71b7-ba46-fb7b10354d91" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsNumberOfPositions_019eb852-e0e8-785d-b94a-cae00df665f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsNumberOfPositions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAbstract_019eb852-e0e8-7c6d-86d8-d153c4c96d28" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsNumberOfPositions_019eb852-e0e8-785d-b94a-cae00df665f1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAbstract_019eb852-e0e8-73a5-861f-71b1ae0550b7" xlink:href="ago-20260630.xsd#ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DeptSecurityAvailableforsaleSecuritiesContinuousUnrealizedLossPositionAbstract_019eb852-e0e8-7933-bcbe-e716abd3a74d" xlink:to="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAbstract_019eb852-e0e8-73a5-861f-71b1ae0550b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019eb852-e0e8-7167-97f4-0980bd9fdfb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAbstract_019eb852-e0e8-73a5-861f-71b1ae0550b7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019eb852-e0e8-7167-97f4-0980bd9fdfb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019eb852-e0e8-7074-bcc0-672f031fa7ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAbstract_019eb852-e0e8-73a5-861f-71b1ae0550b7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019eb852-e0e8-7074-bcc0-672f031fa7ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions_019eb852-e0e8-70ce-82f4-8c52c33bd064" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAbstract_019eb852-e0e8-73a5-861f-71b1ae0550b7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions_019eb852-e0e8-70ce-82f4-8c52c33bd064" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateAbstract_019eb852-e0e8-7221-b863-3541863494b5" xlink:href="ago-20260630.xsd#ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_DeptSecurityAvailableforsaleSecuritiesContinuousUnrealizedLossPositionAbstract_019eb852-e0e8-7933-bcbe-e716abd3a74d" xlink:to="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateAbstract_019eb852-e0e8-7221-b863-3541863494b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019eb852-e0e8-7da0-a5b9-0e997eada832" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateAbstract_019eb852-e0e8-7221-b863-3541863494b5" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019eb852-e0e8-7da0-a5b9-0e997eada832" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019eb852-e0e8-7907-93ed-fb85546dbcb3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateAbstract_019eb852-e0e8-7221-b863-3541863494b5" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019eb852-e0e8-7907-93ed-fb85546dbcb3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_019eb852-e0e8-7322-9009-21c9159c0221" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateAbstract_019eb852-e0e8-7221-b863-3541863494b5" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_019eb852-e0e8-7322-9009-21c9159c0221" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/InvestmentsDistributionofFixedMaturitySecuritiesbyContractualMaturityDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#InvestmentsDistributionofFixedMaturitySecuritiesbyContractualMaturityDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/InvestmentsDistributionofFixedMaturitySecuritiesbyContractualMaturityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb852-e0e8-7e76-a41d-96a6735e02ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7f89-b5e1-7baddec31bad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb852-e0e8-7e76-a41d-96a6735e02ad" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7f89-b5e1-7baddec31bad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7fce-9c28-05a8aefb034e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019eb852-e0e8-7f89-b5e1-7baddec31bad" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7fce-9c28-05a8aefb034e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7fce-9c28-05a8aefb034e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7fce-9c28-05a8aefb034e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7fce-9c28-05a8aefb034e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-772e-b968-0ad05a7771f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7fce-9c28-05a8aefb034e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-772e-b968-0ad05a7771f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-77f2-bec3-fa41eca45349" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-772e-b968-0ad05a7771f3" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-77f2-bec3-fa41eca45349" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7e1d-805d-1ff602a21272" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-772e-b968-0ad05a7771f3" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7e1d-805d-1ff602a21272" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_019eb852-e0e8-706a-93aa-bd3b36068531" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb852-e0e8-7e76-a41d-96a6735e02ad" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_019eb852-e0e8-706a-93aa-bd3b36068531" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_019eb852-e0e8-706a-93aa-bd3b36068531" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis_019eb852-e0e8-7b0c-8fff-dedee0bdb494" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis_019eb852-e0e8-7b0c-8fff-dedee0bdb494" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis_019eb852-e0e8-75e8-886e-0c22841becc9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis_019eb852-e0e8-75e8-886e-0c22841becc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis_019eb852-e0e8-7643-b36d-6c8ca919f1ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis_019eb852-e0e8-7643-b36d-6c8ca919f1ed" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis_019eb852-e0e8-7d55-b51a-0b6429b0ed8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis_019eb852-e0e8-7d55-b51a-0b6429b0ed8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb852-e0e8-70d8-a1c1-e078ff456f68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_019eb852-e0e8-7022-8349-4a55c62c3f23" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb852-e0e8-70d8-a1c1-e078ff456f68" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_019eb852-e0e8-706a-93aa-bd3b36068531" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_019eb852-e0e8-7ef9-b2d1-be3eef2a1111" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_019eb852-e0e8-7ef9-b2d1-be3eef2a1111" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_019eb852-e0e8-7eb3-ac07-212b72767d70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_019eb852-e0e8-7eb3-ac07-212b72767d70" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_019eb852-e0e8-7052-ae9a-8c8e8e4ff517" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_019eb852-e0e8-7052-ae9a-8c8e8e4ff517" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue_019eb852-e0e8-76f0-b294-668aaeff33e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue_019eb852-e0e8-76f0-b294-668aaeff33e6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-765b-8566-3d79f4a3883f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_019eb852-e0e8-7805-a6f5-2658cb795db0" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-765b-8566-3d79f4a3883f" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/InvestmentsNetInvestmentIncomeandEquityinEarningsofInvesteesDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#InvestmentsNetInvestmentIncomeandEquityinEarningsofInvesteesDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/InvestmentsNetInvestmentIncomeandEquityinEarningsofInvesteesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019eb852-e0e8-7d66-96f4-9bb264d14e4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable_019eb852-e0e8-77b0-bb3a-b6c2577b8b04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019eb852-e0e8-7d66-96f4-9bb264d14e4a" xlink:to="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable_019eb852-e0e8-77b0-bb3a-b6c2577b8b04" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-72c5-891f-111b532457d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable_019eb852-e0e8-77b0-bb3a-b6c2577b8b04" xlink:to="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-72c5-891f-111b532457d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-72c5-891f-111b532457d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-72c5-891f-111b532457d4" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-72c5-891f-111b532457d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019eb852-e0e8-72c5-891f-111b532457d4" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019eb852-e0e8-77ac-9010-7caf7041e0ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_us-gaap_FixedMaturitiesMember_019eb852-e0e8-77ac-9010-7caf7041e0ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_019eb852-e0e8-7586-b546-df2c3f8ccf51" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_019eb852-e0e8-7586-b546-df2c3f8ccf51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherInvestedAssetsMember_019eb85b-1b9a-78ac-a3fc-409fed7aedcc" xlink:href="ago-20260630.xsd#ago_OtherInvestedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_ago_OtherInvestedAssetsMember_019eb85b-1b9a-78ac-a3fc-409fed7aedcc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SoundPointCapitalManagementLPMember_019eb852-e0e8-78ff-a641-688759392886" xlink:href="ago-20260630.xsd#ago_SoundPointCapitalManagementLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_ago_SoundPointCapitalManagementLPMember_019eb852-e0e8-78ff-a641-688759392886" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FundsAndOtherInvestmentsMember_019eb852-e0e8-7bd7-a542-b803daa8a087" xlink:href="ago-20260630.xsd#ago_FundsAndOtherInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_ago_FundsAndOtherInvestmentsMember_019eb852-e0e8-7bd7-a542-b803daa8a087" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_InsuredFinancialObligationsLossMitigationSecuritiesMember_019eb852-e0e8-7431-bb66-4e463c750a45" xlink:href="ago-20260630.xsd#ago_InsuredFinancialObligationsLossMitigationSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_ago_InsuredFinancialObligationsLossMitigationSecuritiesMember_019eb852-e0e8-7431-bb66-4e463c750a45" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FixedMaturitiesTradingSecuritiesMember_019eb852-e0e8-7e1b-874b-d277bf806a4f" xlink:href="ago-20260630.xsd#ago_FixedMaturitiesTradingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019eb852-e0e8-75eb-80c8-7798e96297b6" xlink:to="loc_ago_FixedMaturitiesTradingSecuritiesMember_019eb852-e0e8-7e1b-874b-d277bf806a4f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019eb852-e0e8-7d66-96f4-9bb264d14e4a" xlink:to="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndDividendIncomeOperating_019eb852-e0e8-717d-bbee-1f054c19bce2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestAndDividendIncomeOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:to="loc_us-gaap_InterestAndDividendIncomeOperating_019eb852-e0e8-717d-bbee-1f054c19bce2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_019eb852-e0e8-754b-9446-8d599aa235bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:to="loc_us-gaap_InvestmentIncomeInvestmentExpense_019eb852-e0e8-754b-9446-8d599aa235bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019eb852-e0e8-7e2c-88cc-2e8f6621060a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:to="loc_us-gaap_NetInvestmentIncome_019eb852-e0e8-7e2c-88cc-2e8f6621060a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesTradingUnrealizedGainLoss_019eb852-e0e8-776f-a697-39d9ff9ad242" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesTradingUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:to="loc_us-gaap_DebtSecuritiesTradingUnrealizedGainLoss_019eb852-e0e8-776f-a697-39d9ff9ad242" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019eb852-e0e8-7bb8-aa42-ceb6d6a1bc46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019eb852-e0e8-7bb8-aa42-ceb6d6a1bc46" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetLiabilityRecurringBasisStillHeldUnrealizedGainLoss_019eb852-e0e8-7204-a213-a015432bb6f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetLiabilityRecurringBasisStillHeldUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentIncomeNetAbstract_019eb852-e0e8-79ec-aa42-365bfb0793ce" xlink:to="loc_us-gaap_FairValueAssetLiabilityRecurringBasisStillHeldUnrealizedGainLoss_019eb852-e0e8-7204-a213-a015432bb6f2" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/VariableInterestEntitiesAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#VariableInterestEntitiesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/VariableInterestEntitiesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75a4-9031-6ce428a69e78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75a4-9031-6ce428a69e78" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7d6f-b0d5-2c02a6826390" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75a4-9031-6ce428a69e78" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7d6f-b0d5-2c02a6826390" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7d6f-b0d5-2c02a6826390_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7d6f-b0d5-2c02a6826390" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7d6f-b0d5-2c02a6826390_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7455-80ad-c080195c2a10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7d6f-b0d5-2c02a6826390" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7455-80ad-c080195c2a10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-71f7-a11f-e8469ecfcee4" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7455-80ad-c080195c2a10" xlink:to="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-71f7-a11f-e8469ecfcee4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-7f2c-8ac8-9f8fee7f1dc5" xlink:href="ago-20260630.xsd#ago_ConsolidatedInvestmentVehiclesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7455-80ad-c080195c2a10" xlink:to="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-7f2c-8ac8-9f8fee7f1dc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PensionRiskTransfersVariableInterestEntitiesMember_019eb852-e0e8-7e71-a6ea-b0392bfe7695" xlink:href="ago-20260630.xsd#ago_PensionRiskTransfersVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7455-80ad-c080195c2a10" xlink:to="loc_ago_PensionRiskTransfersVariableInterestEntitiesMember_019eb852-e0e8-7e71-a6ea-b0392bfe7695" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-793a-95a2-7a302622b363" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75a4-9031-6ce428a69e78" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-793a-95a2-7a302622b363" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-793a-95a2-7a302622b363_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-793a-95a2-7a302622b363" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-793a-95a2-7a302622b363_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7445-8766-0d71f8fdf766" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-793a-95a2-7a302622b363" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7445-8766-0d71f8fdf766" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-71c8-aa61-a9c8209cd457" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7445-8766-0d71f8fdf766" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-71c8-aa61-a9c8209cd457" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019eb852-e0e8-71f2-9b5c-0ea6eded7ebc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75a4-9031-6ce428a69e78" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019eb852-e0e8-71f2-9b5c-0ea6eded7ebc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019eb852-e0e8-71f2-9b5c-0ea6eded7ebc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019eb852-e0e8-71f2-9b5c-0ea6eded7ebc" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019eb852-e0e8-71f2-9b5c-0ea6eded7ebc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019eb852-e0e8-728d-b288-79cc87723fd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019eb852-e0e8-71f2-9b5c-0ea6eded7ebc" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019eb852-e0e8-728d-b288-79cc87723fd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_SoundPointAgreementMember_019eb852-e0e8-7284-9d19-c6bffc2057f7" xlink:href="ago-20260630.xsd#ago_SoundPointAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019eb852-e0e8-728d-b288-79cc87723fd9" xlink:to="loc_ago_SoundPointAgreementMember_019eb852-e0e8-7284-9d19-c6bffc2057f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityNumberofEntities_019eb852-e0e8-7103-9f5a-5b85f3592017" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityNumberofEntities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_ago_VariableInterestEntityNumberofEntities_019eb852-e0e8-7103-9f5a-5b85f3592017" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMaximumLossExposureAmount_019eb852-e0e8-78b4-b136-5f776eea3f18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMaximumLossExposureAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMaximumLossExposureAmount_019eb852-e0e8-78b4-b136-5f776eea3f18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_019eb852-e0e8-7c91-9a62-c88c681ec3ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_019eb852-e0e8-7c91-9a62-c88c681ec3ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityNumberofEntitiesConsolidated_019eb852-e0e8-79b8-a968-91bd3bd67e8b" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityNumberofEntitiesConsolidated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_ago_VariableInterestEntityNumberofEntitiesConsolidated_019eb852-e0e8-79b8-a968-91bd3bd67e8b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019eb852-e0e8-7c9e-b8fa-70ab3a559e57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_Assets_019eb852-e0e8-7c9e-b8fa-70ab3a559e57" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7609-b7fb-1c59eb709f08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7609-b7fb-1c59eb709f08" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_019fd267-1020-7911-ab2e-8bb928b0c2e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_ShortTermInvestments_019fd267-1020-7911-ab2e-8bb928b0c2e8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019eb852-e0e8-73d7-89fc-b65629fb8de1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_OtherAssets_019eb852-e0e8-73d7-89fc-b65629fb8de1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019eb852-e0e8-79c1-8983-1ac746f1842d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019eb852-e0e8-79c1-8983-1ac746f1842d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_019eb852-e0e8-7d15-b18a-f7bdeba8802c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Cash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_Cash_019eb852-e0e8-7d15-b18a-f7bdeba8802c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityNumberofPoliciesMonitored_019eb852-e0e8-786f-b7aa-36948e48889e" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityNumberofPoliciesMonitored"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_ago_VariableInterestEntityNumberofPoliciesMonitored_019eb852-e0e8-786f-b7aa-36948e48889e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityNumberofPoliciesMonitoredNotWithintheScopeofASC810_019eb852-e0e8-7d0e-8a41-f6885d22ebaf" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityNumberofPoliciesMonitoredNotWithintheScopeofASC810"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_ago_VariableInterestEntityNumberofPoliciesMonitoredNotWithintheScopeofASC810_019eb852-e0e8-7d0e-8a41-f6885d22ebaf" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityNumberofPoliciesthatContainProvisionsforConsolidation_019eb852-e0e8-7f15-8709-5957b8afc602" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityNumberofPoliciesthatContainProvisionsforConsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_ago_VariableInterestEntityNumberofPoliciesthatContainProvisionsforConsolidation_019eb852-e0e8-7f15-8709-5957b8afc602" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount_019eb852-e0e8-7e89-8656-cb67c9c56414" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7a05-a4c8-3065dfe4b195" xlink:to="loc_us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount_019eb852-e0e8-7e89-8656-cb67c9c56414" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/VariableInterestEntitiesConsolidatedFGVIEsByTypeofCollateralDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#VariableInterestEntitiesConsolidatedFGVIEsByTypeofCollateralDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/VariableInterestEntitiesConsolidatedFGVIEsByTypeofCollateralDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7624-ac49-68b3a2d77799" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7624-ac49-68b3a2d77799" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7624-ac49-68b3a2d77799_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7624-ac49-68b3a2d77799" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7624-ac49-68b3a2d77799_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7e44-97c8-0c2e0267ce99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7624-ac49-68b3a2d77799" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7e44-97c8-0c2e0267ce99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7230-a186-3c0529b5f098" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7e44-97c8-0c2e0267ce99" xlink:to="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7230-a186-3c0529b5f098" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7d9c-ad41-0e01af54f3a9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7d9c-ad41-0e01af54f3a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7d9c-ad41-0e01af54f3a9_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7d9c-ad41-0e01af54f3a9" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7d9c-ad41-0e01af54f3a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-710d-bcd5-46ff6ecee892" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7d9c-ad41-0e01af54f3a9" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-710d-bcd5-46ff6ecee892" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-7e97-ae4b-667dfacf6c05" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-710d-bcd5-46ff6ecee892" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-7e97-ae4b-667dfacf6c05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb852-e0e8-704d-9ac5-28a9f1a5bbee" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:to="loc_srt_StatementGeographicalAxis_019eb852-e0e8-704d-9ac5-28a9f1a5bbee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e0e8-704d-9ac5-28a9f1a5bbee_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e0e8-704d-9ac5-28a9f1a5bbee" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e0e8-704d-9ac5-28a9f1a5bbee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb852-e0e8-7458-86ff-3b55c3ec8f76" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb852-e0e8-704d-9ac5-28a9f1a5bbee" xlink:to="loc_srt_SegmentGeographicalDomain_019eb852-e0e8-7458-86ff-3b55c3ec8f76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e0e8-7b51-a0e4-15016443d532" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb852-e0e8-7458-86ff-3b55c3ec8f76" xlink:to="loc_country_US_019eb852-e0e8-7b51-a0e4-15016443d532" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e0e8-7bf7-a34d-72650258f4b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e0e8-7bf7-a34d-72650258f4b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e0e8-7bf7-a34d-72650258f4b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e0e8-7bf7-a34d-72650258f4b4" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e0e8-7bf7-a34d-72650258f4b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e0e8-798e-89c0-c837b4fcfc98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_019eb852-e0e8-7bf7-a34d-72650258f4b4" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e0e8-798e-89c0-c837b4fcfc98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7537-828b-89bfe97d4a90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e0e8-798e-89c0-c837b4fcfc98" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7537-828b-89bfe97d4a90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingOtherMember_019eb852-e0e8-75b2-9908-4a3ff3470490" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnderlyingOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_019eb852-e0e8-798e-89c0-c837b4fcfc98" xlink:to="loc_us-gaap_UnderlyingOtherMember_019eb852-e0e8-75b2-9908-4a3ff3470490" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseStatusAxis_019eb852-e0e8-7445-8687-e9e58736901e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RecourseStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:to="loc_us-gaap_RecourseStatusAxis_019eb852-e0e8-7445-8687-e9e58736901e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseStatusDomain_019eb852-e0e8-7445-8687-e9e58736901e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RecourseStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RecourseStatusAxis_019eb852-e0e8-7445-8687-e9e58736901e" xlink:to="loc_us-gaap_RecourseStatusDomain_019eb852-e0e8-7445-8687-e9e58736901e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseStatusDomain_019eb852-e0e8-70a4-896f-2abd0d746a77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RecourseStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RecourseStatusAxis_019eb852-e0e8-7445-8687-e9e58736901e" xlink:to="loc_us-gaap_RecourseStatusDomain_019eb852-e0e8-70a4-896f-2abd0d746a77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseMember_019eb852-e0e8-7021-9009-37ab9d4156ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RecourseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RecourseStatusDomain_019eb852-e0e8-70a4-896f-2abd0d746a77" xlink:to="loc_us-gaap_RecourseMember_019eb852-e0e8-7021-9009-37ab9d4156ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecourseMember_019eb852-e0e8-7e4b-ba53-ac5f48dfc16f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrecourseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RecourseStatusDomain_019eb852-e0e8-70a4-896f-2abd0d746a77" xlink:to="loc_us-gaap_NonrecourseMember_019eb852-e0e8-7e4b-ba53-ac5f48dfc16f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-73fc-b13b-1b3af1db4a34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-7f6f-9792-a07bc94c5f9f" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-73fc-b13b-1b3af1db4a34" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-73fc-b13b-1b3af1db4a34_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-73fc-b13b-1b3af1db4a34" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-73fc-b13b-1b3af1db4a34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7ef1-8344-49565b3cb9d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-73fc-b13b-1b3af1db4a34" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7ef1-8344-49565b3cb9d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-785e-9e60-a5c34ca7bac1" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7ef1-8344-49565b3cb9d7" xlink:to="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-785e-9e60-a5c34ca7bac1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019eb852-e0e8-7229-8e10-0d500b12c028" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:to="loc_us-gaap_Assets_019eb852-e0e8-7229-8e10-0d500b12c028" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019eb852-e0e8-7275-aa53-78558b646352" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:to="loc_us-gaap_Liabilities_019eb852-e0e8-7275-aa53-78558b646352" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019eb852-e0e8-751c-bdcb-091f3c27fd3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019eb852-e0e8-751c-bdcb-091f3c27fd3a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019eb852-e0e8-7157-8a57-ec36db5328a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019eb852-e0e8-7157-8a57-ec36db5328a8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNet_019eb852-e0e8-75d9-8de5-bb7e70951a9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerAssetNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7527-b090-fa314dfc54e7" xlink:to="loc_us-gaap_ContractWithCustomerAssetNet_019eb852-e0e8-75d9-8de5-bb7e70951a9d" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/VariableInterestEntitiesUnpaidPrincipalDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#VariableInterestEntitiesUnpaidPrincipalDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/VariableInterestEntitiesUnpaidPrincipalDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75fc-a075-e89cc1da72b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75fc-a075-e89cc1da72b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7835-ab40-68c98aa6f315" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75fc-a075-e89cc1da72b7" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7835-ab40-68c98aa6f315" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7835-ab40-68c98aa6f315_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7835-ab40-68c98aa6f315" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7835-ab40-68c98aa6f315_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-70a4-ac89-e4bb78d9f22a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7835-ab40-68c98aa6f315" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-70a4-ac89-e4bb78d9f22a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-709f-a385-cd868ccaad13" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-70a4-ac89-e4bb78d9f22a" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-709f-a385-cd868ccaad13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7154-8f76-a63201126a75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75fc-a075-e89cc1da72b7" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7154-8f76-a63201126a75" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7154-8f76-a63201126a75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7154-8f76-a63201126a75" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7154-8f76-a63201126a75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-72d7-8994-3aa2350c3a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7154-8f76-a63201126a75" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-72d7-8994-3aa2350c3a6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7570-8771-50c5ccd0075f" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-72d7-8994-3aa2350c3a6b" xlink:to="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7570-8771-50c5ccd0075f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-7d72-88b9-a863c4e03974" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019eb852-e0e8-75fc-a075-e89cc1da72b7" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-7d72-88b9-a863c4e03974" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7d72-88b9-a863c4e03974_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-7d72-88b9-a863c4e03974" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7d72-88b9-a863c4e03974_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-73ec-8b6a-715eb7eb7e74" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-7d72-88b9-a863c4e03974" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-73ec-8b6a-715eb7eb7e74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7bfc-9c1c-9790b16ac68c" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-73ec-8b6a-715eb7eb7e74" xlink:to="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7bfc-9c1c-9790b16ac68c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables_019eb852-e0e8-7d5c-ad4d-f3ea9e60f32c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:to="loc_us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables_019eb852-e0e8-7d5c-ad4d-f3ea9e60f32c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueOptionLoansHeldasLiabilitiesAggregateDifferenceWithRecourse_019eb852-e0e8-7f03-a70b-e8a9e3b81130" xlink:href="ago-20260630.xsd#ago_FairValueOptionLoansHeldasLiabilitiesAggregateDifferenceWithRecourse"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:to="loc_ago_FairValueOptionLoansHeldasLiabilitiesAggregateDifferenceWithRecourse_019eb852-e0e8-7f03-a70b-e8a9e3b81130" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueOptionLoansHeldasLiabilitiesAggregateDifferenceWithoutRecourse_019eb852-e0e8-738b-8bc3-2579d1736a2a" xlink:href="ago-20260630.xsd#ago_FairValueOptionLoansHeldasLiabilitiesAggregateDifferenceWithoutRecourse"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:to="loc_ago_FairValueOptionLoansHeldasLiabilitiesAggregateDifferenceWithoutRecourse_019eb852-e0e8-738b-8bc3-2579d1736a2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue_019eb852-e0e8-77e2-8aa8-d2b2e70f83a5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:to="loc_us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue_019eb852-e0e8-77e2-8aa8-d2b2e70f83a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueOptionLiabilitieswithRecourseUnpaidPrincipalBalance_019eb852-e0e8-7423-a114-42c559dc135e" xlink:href="ago-20260630.xsd#ago_FairValueOptionLiabilitieswithRecourseUnpaidPrincipalBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019eb852-e0e8-7541-9ef9-d977ba6aefaa" xlink:to="loc_ago_FairValueOptionLiabilitieswithRecourseUnpaidPrincipalBalance_019eb852-e0e8-7423-a114-42c559dc135e" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/FairValueMeasurementAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#FairValueMeasurementAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/FairValueMeasurementAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-7fd2-8489-1190e2f376a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-7fd2-8489-1190e2f376a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019eb852-e0e8-7209-9120-a62fa0e70ff4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-7fd2-8489-1190e2f376a2" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019eb852-e0e8-7209-9120-a62fa0e70ff4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019eb852-e0e8-7209-9120-a62fa0e70ff4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019eb852-e0e8-7209-9120-a62fa0e70ff4" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019eb852-e0e8-7209-9120-a62fa0e70ff4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019eb852-e0e8-729f-85c0-5badebb0f780" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019eb852-e0e8-7209-9120-a62fa0e70ff4" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019eb852-e0e8-729f-85c0-5badebb0f780" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019eb852-e0e8-7c41-9da9-a181d00248d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019eb852-e0e8-729f-85c0-5badebb0f780" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019eb852-e0e8-7c41-9da9-a181d00248d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-70da-8b4a-7f7201253368" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-7fd2-8489-1190e2f376a2" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-70da-8b4a-7f7201253368" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-70da-8b4a-7f7201253368_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-70da-8b4a-7f7201253368" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-70da-8b4a-7f7201253368_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-7da5-96a5-8973a00f2fff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-70da-8b4a-7f7201253368" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-7da5-96a5-8973a00f2fff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019eb852-e0e8-7517-b2d6-a8555b41dd99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-7da5-96a5-8973a00f2fff" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019eb852-e0e8-7517-b2d6-a8555b41dd99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019eb852-e0e8-792d-8f13-cb1cd7fcf22b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-7fd2-8489-1190e2f376a2" xlink:to="loc_dei_LegalEntityAxis_019eb852-e0e8-792d-8f13-cb1cd7fcf22b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e0e8-792d-8f13-cb1cd7fcf22b_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019eb852-e0e8-792d-8f13-cb1cd7fcf22b" xlink:to="loc_dei_EntityDomain_019eb852-e0e8-792d-8f13-cb1cd7fcf22b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019eb852-e0e8-72dc-9caf-560716f4394a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019eb852-e0e8-792d-8f13-cb1cd7fcf22b" xlink:to="loc_dei_EntityDomain_019eb852-e0e8-72dc-9caf-560716f4394a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssuredGuarantyIncMember_019eb852-e0e8-7eab-a77c-86359a325843" xlink:href="ago-20260630.xsd#ago_AssuredGuarantyIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019eb852-e0e8-72dc-9caf-560716f4394a" xlink:to="loc_ago_AssuredGuarantyIncMember_019eb852-e0e8-7eab-a77c-86359a325843" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesByContractTypeAxis_019eb852-e0e8-783a-88aa-8bdac9f3f409" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesByContractTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-7fd2-8489-1190e2f376a2" xlink:to="loc_us-gaap_CreditDerivativesByContractTypeAxis_019eb852-e0e8-783a-88aa-8bdac9f3f409" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesContractTypeDomain_019eb852-e0e8-783a-88aa-8bdac9f3f409_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditDerivativesByContractTypeAxis_019eb852-e0e8-783a-88aa-8bdac9f3f409" xlink:to="loc_us-gaap_CreditDerivativesContractTypeDomain_019eb852-e0e8-783a-88aa-8bdac9f3f409_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesContractTypeDomain_019eb852-e0e8-778b-ad01-c5118999b140" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDerivativesContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditDerivativesByContractTypeAxis_019eb852-e0e8-783a-88aa-8bdac9f3f409" xlink:to="loc_us-gaap_CreditDerivativesContractTypeDomain_019eb852-e0e8-778b-ad01-c5118999b140" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDefaultSwapMember_019eb852-e0e8-787a-af92-0b182a224050" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditDefaultSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesContractTypeDomain_019eb852-e0e8-778b-ad01-c5118999b140" xlink:to="loc_us-gaap_CreditDefaultSwapMember_019eb852-e0e8-787a-af92-0b182a224050" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AvailableforsaleDebtSecuritiesNumberofInstruments_019eb852-e0e8-7973-a113-e4dfa5e00496" xlink:href="ago-20260630.xsd#ago_AvailableforsaleDebtSecuritiesNumberofInstruments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:to="loc_ago_AvailableforsaleDebtSecuritiesNumberofInstruments_019eb852-e0e8-7973-a113-e4dfa5e00496" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_PercentageOfCDSContractsFairValuedUsingMinimumPremium_019eb852-e0e8-7db7-a2b3-2041cc382f40" xlink:href="ago-20260630.xsd#ago_PercentageOfCDSContractsFairValuedUsingMinimumPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:to="loc_ago_PercentageOfCDSContractsFairValuedUsingMinimumPremium_019eb852-e0e8-7db7-a2b3-2041cc382f40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialInstrumentsSubjecttoMandatoryRedemptionSettlementTermsNumberofCustodialTrusts_019eb852-e0e8-71fd-988f-9ac0a59c8c1b" xlink:href="ago-20260630.xsd#ago_FinancialInstrumentsSubjecttoMandatoryRedemptionSettlementTermsNumberofCustodialTrusts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:to="loc_ago_FinancialInstrumentsSubjecttoMandatoryRedemptionSettlementTermsNumberofCustodialTrusts_019eb852-e0e8-71fd-988f-9ac0a59c8c1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesSubjectToMandatoryRedemptionSettlementTermsAmount_019eb852-e0e8-768c-b3e2-da7b3e6c8859" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesSubjectToMandatoryRedemptionSettlementTermsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:to="loc_us-gaap_SharesSubjectToMandatoryRedemptionSettlementTermsAmount_019eb852-e0e8-768c-b3e2-da7b3e6c8859" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesSubjectToMandatoryRedemptionSettlementTermsMaximumAmount_019eb852-e0e8-74d4-a647-92be9e90d060" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesSubjectToMandatoryRedemptionSettlementTermsMaximumAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-72f0-901b-9f33f4c915b7" xlink:to="loc_us-gaap_SharesSubjectToMandatoryRedemptionSettlementTermsMaximumAmount_019eb852-e0e8-74d4-a647-92be9e90d060" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/FairValueMeasurementFinancialInstrumentsCarriedatFairValueDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#FairValueMeasurementFinancialInstrumentsCarriedatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/FairValueMeasurementFinancialInstrumentsCarriedatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019eb852-e0e8-7d9e-8f85-7691d7e525a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019eb852-e0e8-7b62-a0be-947bbe821f35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019eb852-e0e8-7d9e-8f85-7691d7e525a3" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019eb852-e0e8-7b62-a0be-947bbe821f35" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-7bc4-88b9-94218d466e5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019eb852-e0e8-7b62-a0be-947bbe821f35" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-7bc4-88b9-94218d466e5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-7bc4-88b9-94218d466e5f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-7bc4-88b9-94218d466e5f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-7bc4-88b9-94218d466e5f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-756c-b2d0-7221356d346f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-7bc4-88b9-94218d466e5f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-756c-b2d0-7221356d346f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019eb852-e0e8-71f2-8468-8e65026ca3d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-756c-b2d0-7221356d346f" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019eb852-e0e8-71f2-8468-8e65026ca3d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019eb852-e0e8-7545-956d-4850e34e923a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-756c-b2d0-7221356d346f" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019eb852-e0e8-7545-956d-4850e34e923a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019eb852-e0e8-76d4-bc2b-cfacbac2577e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-756c-b2d0-7221356d346f" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019eb852-e0e8-76d4-bc2b-cfacbac2577e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-72e9-a068-7478774f1862" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019eb852-e0e8-7b62-a0be-947bbe821f35" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-72e9-a068-7478774f1862" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-72e9-a068-7478774f1862_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-72e9-a068-7478774f1862" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-72e9-a068-7478774f1862_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-72e9-a068-7478774f1862" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7bd5-ae5e-069823475b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7bd5-ae5e-069823475b5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019eb852-e0e8-7c49-a95a-6d16f899bccc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019eb852-e0e8-7c49-a95a-6d16f899bccc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-7616-b6e4-e1de3582167c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-7616-b6e4-e1de3582167c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7725-a2ad-fc47dfc75580" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7725-a2ad-fc47dfc75580" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7fc2-8ee1-00e8bb4ca32a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019eb852-e0e8-7fc2-8ee1-00e8bb4ca32a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019eb852-e0e8-7311-b889-1fd5fac50d06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019eb852-e0e8-7311-b889-1fd5fac50d06" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019eb852-e0e8-7496-b887-fb97f91909bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-70e4-911d-17a3b3657c6f" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019eb852-e0e8-7496-b887-fb97f91909bb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7f7c-bf54-7d95ece2d97d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019eb852-e0e8-7b62-a0be-947bbe821f35" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7f7c-bf54-7d95ece2d97d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7f7c-bf54-7d95ece2d97d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7f7c-bf54-7d95ece2d97d" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7f7c-bf54-7d95ece2d97d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-784b-92a5-2b00eb387eb5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7f7c-bf54-7d95ece2d97d" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-784b-92a5-2b00eb387eb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-799b-81b6-4fe4170ee0f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-784b-92a5-2b00eb387eb5" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-799b-81b6-4fe4170ee0f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019eb852-e0e8-7d9e-8f85-7691d7e525a3" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-76c8-b86a-65b613decac4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-76c8-b86a-65b613decac4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-7ed2-bc3f-dc79e281c073" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-7ed2-bc3f-dc79e281c073" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermInvestments_019fd27c-116d-7ea8-9e13-67163114d377" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_OtherShortTermInvestments_019fd27c-116d-7ea8-9e13-67163114d377" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherInvestmentsFairValueDisclosure_019eb852-e0e8-746e-9a6a-0c9d0333809e" xlink:href="ago-20260630.xsd#ago_OtherInvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_ago_OtherInvestmentsFairValueDisclosure_019eb852-e0e8-746e-9a6a-0c9d0333809e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FundsHeldUnderReinsuranceAgreementsAsset_019eb852-e0e8-7569-9734-002cad37acbf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FundsHeldUnderReinsuranceAgreementsAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_FundsHeldUnderReinsuranceAgreementsAsset_019eb852-e0e8-7569-9734-002cad37acbf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019eb852-e0e8-7507-b52e-65cc181ee0ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019eb852-e0e8-7507-b52e-65cc181ee0ec" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019eb852-e0e8-7448-a705-9bfdc2f447d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019eb852-e0e8-7448-a705-9bfdc2f447d3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_019eb852-e0e8-7f87-90b2-53e0dd7138f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019eb852-e0e8-7905-961f-0b8e39ef3ae3" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_019eb852-e0e8-7f87-90b2-53e0dd7138f5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019eb852-e0e8-745f-85bd-a7625c7164d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019eb852-e0e8-7d9e-8f85-7691d7e525a3" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019eb852-e0e8-745f-85bd-a7625c7164d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesFairValueDisclosure_019eb852-e0e8-7631-8103-8d0dcaa4cda5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019eb852-e0e8-745f-85bd-a7625c7164d3" xlink:to="loc_us-gaap_OtherLiabilitiesFairValueDisclosure_019eb852-e0e8-7631-8103-8d0dcaa4cda5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019eb852-e0e8-7ac0-9455-6ae84cd46932" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019eb852-e0e8-745f-85bd-a7625c7164d3" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019eb852-e0e8-7ac0-9455-6ae84cd46932" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/FairValueMeasurementFairValueLevel3RollforwardRecurringBasisDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#FairValueMeasurementFairValueLevel3RollforwardRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/FairValueMeasurementFairValueLevel3RollforwardRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dee-a7d6-63425893172a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dee-a7d6-63425893172a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7325-90cc-5ed948405ec7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7325-90cc-5ed948405ec7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-78f4-8132-aa01dea6a394" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-78f4-8132-aa01dea6a394" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-76f6-9557-eb0257d8e9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-76f6-9557-eb0257d8e9b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019eb852-e0e8-7a1a-a88e-bb7e7e82ecdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019eb852-e0e8-7a1a-a88e-bb7e7e82ecdc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FixedMaturitiesTradingSecuritiesMember_019eb852-e0e8-77e5-b5cb-0c27a5f54885" xlink:href="ago-20260630.xsd#ago_FixedMaturitiesTradingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_ago_FixedMaturitiesTradingSecuritiesMember_019eb852-e0e8-77e5-b5cb-0c27a5f54885" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FundsWithheldMember_019eb852-e0e8-7f53-8494-2334e4e29928" xlink:href="ago-20260630.xsd#ago_FundsWithheldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_ago_FundsWithheldMember_019eb852-e0e8-7f53-8494-2334e4e29928" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-796d-b9d3-a94e03ee9471_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-796d-b9d3-a94e03ee9471_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019eb852-e0e8-7024-a13c-6b5a11370e48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_us-gaap_FixedMaturitiesMember_019eb852-e0e8-7024-a13c-6b5a11370e48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityAssetsMember_019eb852-e0e8-7f45-81f9-6dd664a2b690" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_ago_VariableInterestEntityAssetsMember_019eb852-e0e8-7f45-81f9-6dd664a2b690" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-73aa-ad9b-d847d5fffed4" xlink:href="ago-20260630.xsd#ago_ConsolidatedInvestmentVehiclesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-73aa-ad9b-d847d5fffed4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherAssetsandOtherInvestedAssetsMember_019eb852-e0e8-78b7-aad0-f374205d9c9a" xlink:href="ago-20260630.xsd#ago_OtherAssetsandOtherInvestedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_ago_OtherAssetsandOtherInvestedAssetsMember_019eb852-e0e8-78b7-aad0-f374205d9c9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeBalanceAxis_019eb852-e0e8-7f01-b96f-d65eeba54914" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:to="loc_us-gaap_OtherComprehensiveIncomeBalanceAxis_019eb852-e0e8-7f01-b96f-d65eeba54914" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019eb852-e0e8-7c28-8163-a9016049dc0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019eb852-e0e8-7c28-8163-a9016049dc0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAcquired_019eb852-e0e8-73cf-9eea-2bb438f63d6f" xlink:href="ago-20260630.xsd#ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAcquired_019eb852-e0e8-73cf-9eea-2bb438f63d6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:href="ago-20260630.xsd#ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019eb852-e0e8-7613-a7aa-1fb29a972658" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019eb852-e0e8-7613-a7aa-1fb29a972658" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019eb852-e0e8-7328-85f9-8c87bb7fafc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019eb852-e0e8-7328-85f9-8c87bb7fafc8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019eb852-e0e8-7060-8810-fdc41bb6e800" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019eb852-e0e8-7060-8810-fdc41bb6e800" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019eb852-e0e8-7efb-b245-695617007be2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019eb852-e0e8-7efb-b245-695617007be2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019eb852-e0e8-7ed8-a9db-6d9298d68275" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019eb852-e0e8-7ed8-a9db-6d9298d68275" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisAssetConsolidations_019f19ae-1d42-7875-beeb-f0c3314ebb68" xlink:href="ago-20260630.xsd#ago_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisAssetConsolidations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisAssetConsolidations_019f19ae-1d42-7875-beeb-f0c3314ebb68" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetDeconsolidations_019eb852-e0e8-75df-a747-11f035597fbf" xlink:href="ago-20260630.xsd#ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetDeconsolidations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetDeconsolidations_019eb852-e0e8-75df-a747-11f035597fbf" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019eb852-e0e8-781e-959e-d9ac38d25c9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019eb852-e0e8-781e-959e-d9ac38d25c9d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019eb852-e0e8-7207-828f-b5e1b8902485" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-7ddd-83c1-7d1e7804fd21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-7ddd-83c1-7d1e7804fd21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-734b-b7a0-ce8731ebede6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-7ddb-98fc-484cd261769f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-734b-b7a0-ce8731ebede6" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-7ddb-98fc-484cd261769f" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e0e8-771e-b0ef-fe36ca3499ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-7ddb-98fc-484cd261769f" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e0e8-771e-b0ef-fe36ca3499ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e0e8-771e-b0ef-fe36ca3499ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e0e8-771e-b0ef-fe36ca3499ce" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e0e8-771e-b0ef-fe36ca3499ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e0e8-77e5-9d08-72c58956eb97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019eb852-e0e8-771e-b0ef-fe36ca3499ce" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e0e8-77e5-9d08-72c58956eb97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditRiskContractMember_019eb852-e0e8-7dbe-9894-a7ff695ec91e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditRiskContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019eb852-e0e8-77e5-9d08-72c58956eb97" xlink:to="loc_us-gaap_CreditRiskContractMember_019eb852-e0e8-7dbe-9894-a7ff695ec91e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_019eb852-e0e8-7975-9e9f-d0cb77fad596" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-734b-b7a0-ce8731ebede6" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_019eb852-e0e8-7975-9e9f-d0cb77fad596" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_019eb852-e0e8-71ed-9286-10023b09b2ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_019eb852-e0e8-7975-9e9f-d0cb77fad596" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_019eb852-e0e8-71ed-9286-10023b09b2ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsNetDerivativeAssetLiabilityAbstract_019eb852-e0e8-776c-92dc-4b2904aaa61f" xlink:href="ago-20260630.xsd#ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsNetDerivativeAssetLiabilityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_019eb852-e0e8-7975-9e9f-d0cb77fad596" xlink:to="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsNetDerivativeAssetLiabilityAbstract_019eb852-e0e8-776c-92dc-4b2904aaa61f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_019eb852-e0e8-7f55-be69-34c1b1aabcbb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsNetDerivativeAssetLiabilityAbstract_019eb852-e0e8-776c-92dc-4b2904aaa61f" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_019eb852-e0e8-7f55-be69-34c1b1aabcbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInOtherComprehensiveIncomeLoss_019eb852-e0e8-7f24-9696-470becded52c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInOtherComprehensiveIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsNetDerivativeAssetLiabilityAbstract_019eb852-e0e8-776c-92dc-4b2904aaa61f" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInOtherComprehensiveIncomeLoss_019eb852-e0e8-7f24-9696-470becded52c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements_019eb852-e0e8-70ee-a236-228023fdd2f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_019eb852-e0e8-7975-9e9f-d0cb77fad596" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements_019eb852-e0e8-70ee-a236-228023fdd2f0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_019eb852-e0e8-7061-8956-4d1becf3a953" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-7682-abbb-48dc158a60f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-734b-b7a0-ce8731ebede6" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-7682-abbb-48dc158a60f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7e51-8161-6715fbe16ea5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-7764-9232-8df3752a0b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7e51-8161-6715fbe16ea5" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-7764-9232-8df3752a0b3a" xlink:type="arc" order="3" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-75bb-8512-4c06c3679981" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-7764-9232-8df3752a0b3a" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-75bb-8512-4c06c3679981" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-75bb-8512-4c06c3679981_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-75bb-8512-4c06c3679981" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-75bb-8512-4c06c3679981_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7288-b5c8-bae9daa0be0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019eb852-e0e8-75bb-8512-4c06c3679981" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7288-b5c8-bae9daa0be0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7c74-b967-acfc35086ccd" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyVariableInterestEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019eb852-e0e8-7288-b5c8-bae9daa0be0a" xlink:to="loc_ago_FinancialGuarantyVariableInterestEntitiesMember_019eb852-e0e8-7c74-b967-acfc35086ccd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-782a-ae84-71913d7869dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7e51-8161-6715fbe16ea5" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-782a-ae84-71913d7869dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019eb852-e0e8-7ed6-a7be-e73a6bd96aa9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-782a-ae84-71913d7869dd" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019eb852-e0e8-7ed6-a7be-e73a6bd96aa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsLiabilitiesAbstract_019eb852-e0e8-7cc7-8bf3-73b1ed2b19fb" xlink:href="ago-20260630.xsd#ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-782a-ae84-71913d7869dd" xlink:to="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsLiabilitiesAbstract_019eb852-e0e8-7cc7-8bf3-73b1ed2b19fb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019eb852-e0e8-7cce-85df-6b263cd58e44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsLiabilitiesAbstract_019eb852-e0e8-7cc7-8bf3-73b1ed2b19fb" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019eb852-e0e8-7cce-85df-6b263cd58e44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_019eb852-e0e8-7997-b5ba-937a37fd4374" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsLiabilitiesAbstract_019eb852-e0e8-7cc7-8bf3-73b1ed2b19fb" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_019eb852-e0e8-7997-b5ba-937a37fd4374" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_019eb852-e0e8-76f3-9d0f-e7fc1f5ef042" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-782a-ae84-71913d7869dd" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_019eb852-e0e8-76f3-9d0f-e7fc1f5ef042" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019eb852-e0e8-7e45-bfc7-f8874bb32cab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-70ec-bda4-f809f8072451" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7e51-8161-6715fbe16ea5" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-70ec-bda4-f809f8072451" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci_019eb852-e0e8-763f-b10e-1067b54fee67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7e51-8161-6715fbe16ea5" xlink:to="loc_us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci_019eb852-e0e8-763f-b10e-1067b54fee67" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/FairValueMeasurementFairValueLevel3RollforwardRecurringBasisDetails_1" xlink:type="simple" xlink:href="ago-20260630.xsd#FairValueMeasurementFairValueLevel3RollforwardRecurringBasisDetails_1"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/FairValueMeasurementFairValueLevel3RollforwardRecurringBasisDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dee-a7d6-63425893172a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dee-a7d6-63425893172a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7dee-a7d6-63425893172a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7325-90cc-5ed948405ec7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7325-90cc-5ed948405ec7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-78f4-8132-aa01dea6a394" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-78f4-8132-aa01dea6a394" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-76f6-9557-eb0257d8e9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-76f6-9557-eb0257d8e9b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019eb852-e0e8-7a1a-a88e-bb7e7e82ecdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019eb852-e0e8-7a1a-a88e-bb7e7e82ecdc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FixedMaturitiesTradingSecuritiesMember_019eb852-e0e8-77e5-b5cb-0c27a5f54885" xlink:href="ago-20260630.xsd#ago_FixedMaturitiesTradingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_ago_FixedMaturitiesTradingSecuritiesMember_019eb852-e0e8-77e5-b5cb-0c27a5f54885" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FundsWithheldMember_019eb852-e0e8-7f53-8494-2334e4e29928" xlink:href="ago-20260630.xsd#ago_FundsWithheldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7758-be19-d48cbc012d5b" xlink:to="loc_ago_FundsWithheldMember_019eb852-e0e8-7f53-8494-2334e4e29928" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019eb852-e0e8-79ac-81e6-751af4463ace" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-796d-b9d3-a94e03ee9471_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-796d-b9d3-a94e03ee9471_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-796d-b9d3-a94e03ee9471" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019eb852-e0e8-7024-a13c-6b5a11370e48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_us-gaap_FixedMaturitiesMember_019eb852-e0e8-7024-a13c-6b5a11370e48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_VariableInterestEntityAssetsMember_019eb852-e0e8-7f45-81f9-6dd664a2b690" xlink:href="ago-20260630.xsd#ago_VariableInterestEntityAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_ago_VariableInterestEntityAssetsMember_019eb852-e0e8-7f45-81f9-6dd664a2b690" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-73aa-ad9b-d847d5fffed4" xlink:href="ago-20260630.xsd#ago_ConsolidatedInvestmentVehiclesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-73aa-ad9b-d847d5fffed4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherAssetsandOtherInvestedAssetsMember_019eb852-e0e8-78b7-aad0-f374205d9c9a" xlink:href="ago-20260630.xsd#ago_OtherAssetsandOtherInvestedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7f02-a928-144973edc398" xlink:to="loc_ago_OtherAssetsandOtherInvestedAssetsMember_019eb852-e0e8-78b7-aad0-f374205d9c9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019eb852-e0e8-7c28-8163-a9016049dc0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019eb852-e0e8-7c28-8163-a9016049dc0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAcquired_019eb852-e0e8-73cf-9eea-2bb438f63d6f" xlink:href="ago-20260630.xsd#ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAcquired_019eb852-e0e8-73cf-9eea-2bb438f63d6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:href="ago-20260630.xsd#ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019eb852-e0e8-7613-a7aa-1fb29a972658" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019eb852-e0e8-7613-a7aa-1fb29a972658" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019eb852-e0e8-7328-85f9-8c87bb7fafc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_TotalPretaxRealizedAndUnrealizedGainsLossesRecordedAsAssetsAbstract_019eb852-e0e8-7740-996f-ae41dd83645f" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019eb852-e0e8-7328-85f9-8c87bb7fafc8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019eb852-e0e8-7060-8810-fdc41bb6e800" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019eb852-e0e8-7060-8810-fdc41bb6e800" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019eb852-e0e8-7efb-b245-695617007be2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019eb852-e0e8-7efb-b245-695617007be2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019eb852-e0e8-7ed8-a9db-6d9298d68275" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019eb852-e0e8-7ed8-a9db-6d9298d68275" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisAssetConsolidations_019f19ae-1d42-7875-beeb-f0c3314ebb68" xlink:href="ago-20260630.xsd#ago_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisAssetConsolidations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisAssetConsolidations_019f19ae-1d42-7875-beeb-f0c3314ebb68" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetDeconsolidations_019eb852-e0e8-75df-a747-11f035597fbf" xlink:href="ago-20260630.xsd#ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetDeconsolidations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_ago_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetDeconsolidations_019eb852-e0e8-75df-a747-11f035597fbf" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019eb852-e0e8-781e-959e-d9ac38d25c9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019eb852-e0e8-7f14-818d-bf1654babcdc" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019eb852-e0e8-781e-959e-d9ac38d25c9d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019eb852-e0e8-7207-828f-b5e1b8902485" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-7ddd-83c1-7d1e7804fd21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019eb852-e0e8-7d88-9583-2f6b32bd12d1" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019eb852-e0e8-7ddd-83c1-7d1e7804fd21" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/FairValueMeasurementQuantitativeInformationAssetsLiabilitiesDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#FairValueMeasurementQuantitativeInformationAssetsLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/FairValueMeasurementQuantitativeInformationAssetsLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7e85-acf7-e27e1d17fd79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7e85-acf7-e27e1d17fd79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7e85-acf7-e27e1d17fd79_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7e85-acf7-e27e1d17fd79" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-7e85-acf7-e27e1d17fd79_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-75af-a6d6-e5995c34bd53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019eb852-e0e8-7e85-acf7-e27e1d17fd79" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-75af-a6d6-e5995c34bd53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-7af2-aa8e-8a9097630881" xlink:href="ago-20260630.xsd#ago_ConsolidatedInvestmentVehiclesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-75af-a6d6-e5995c34bd53" xlink:to="loc_ago_ConsolidatedInvestmentVehiclesMember_019eb852-e0e8-7af2-aa8e-8a9097630881" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherInvestedAssetsMember_019eb852-e0e8-70ba-b71d-f3f8b094acd8" xlink:href="ago-20260630.xsd#ago_OtherInvestedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019eb852-e0e8-75af-a6d6-e5995c34bd53" xlink:to="loc_ago_OtherInvestedAssetsMember_019eb852-e0e8-70ba-b71d-f3f8b094acd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_019eb852-e0e8-738b-9881-bf254720c572" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_019eb852-e0e8-738b-9881-bf254720c572" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-738b-9881-bf254720c572_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_019eb852-e0e8-738b-9881-bf254720c572" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-738b-9881-bf254720c572_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_019eb852-e0e8-738b-9881-bf254720c572" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MeasurementInputYieldMember_019eb852-e0e8-7ebc-bce3-4e4b7ea6514c" xlink:href="ago-20260630.xsd#ago_MeasurementInputYieldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_MeasurementInputYieldMember_019eb852-e0e8-7ebc-bce3-4e4b7ea6514c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputPrepaymentRateMember_019eb852-e0e8-77c2-997b-c910a670e1fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputPrepaymentRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_us-gaap_MeasurementInputPrepaymentRateMember_019eb852-e0e8-77c2-997b-c910a670e1fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDefaultRateMember_019eb852-e0e8-7da2-92eb-947a43dc8ce7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputDefaultRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_us-gaap_MeasurementInputDefaultRateMember_019eb852-e0e8-7da2-92eb-947a43dc8ce7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputLossSeverityMember_019eb852-e0e8-76ef-8633-16cf0d6476cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputLossSeverityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_us-gaap_MeasurementInputLossSeverityMember_019eb852-e0e8-76ef-8633-16cf0d6476cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_019eb852-e0e8-7aa8-97d3-66ec77571f54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_019eb852-e0e8-7aa8-97d3-66ec77571f54" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MeasurementInputPriceToEarningsMember_019eb852-e0e8-7e40-90af-fa76d6e1ef0b" xlink:href="ago-20260630.xsd#ago_MeasurementInputPriceToEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_MeasurementInputPriceToEarningsMember_019eb852-e0e8-7e40-90af-fa76d6e1ef0b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputLongTermRevenueGrowthRateMember_019eb852-e0e8-70c0-a5b0-2f99d043cd19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputLongTermRevenueGrowthRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_us-gaap_MeasurementInputLongTermRevenueGrowthRateMember_019eb852-e0e8-70c0-a5b0-2f99d043cd19" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MeasurementInputImpliedYieldMember_019eb852-e0e8-7115-b0c4-875a1f65fdcf" xlink:href="ago-20260630.xsd#ago_MeasurementInputImpliedYieldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_MeasurementInputImpliedYieldMember_019eb852-e0e8-7115-b0c4-875a1f65fdcf" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedTermMember_019eb852-e0e8-7d39-a2eb-0a74b95da7e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputExpectedTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_019eb852-e0e8-7d39-a2eb-0a74b95da7e4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_HedgeCostMember_019eb852-e0e8-7d4e-9693-1594ed9269b0" xlink:href="ago-20260630.xsd#ago_HedgeCostMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_HedgeCostMember_019eb852-e0e8-7d4e-9693-1594ed9269b0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_BankProfitMember_019eb852-e0e8-7e1f-8d6f-4fe6cb5cbd2c" xlink:href="ago-20260630.xsd#ago_BankProfitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_BankProfitMember_019eb852-e0e8-7e1f-8d6f-4fe6cb5cbd2c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MeasurementInputExitMultiplePriceToBookMember_019eb852-e0e8-7b52-b9d3-46bafa6daabb" xlink:href="ago-20260630.xsd#ago_MeasurementInputExitMultiplePriceToBookMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_MeasurementInputExitMultiplePriceToBookMember_019eb852-e0e8-7b52-b9d3-46bafa6daabb" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_MeasurementInputExitMultiplePriceToEarningsMember_019eb852-e0e8-72a8-8c92-0743b8e491a5" xlink:href="ago-20260630.xsd#ago_MeasurementInputExitMultiplePriceToEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019eb852-e0e8-7bb9-b221-2dacd5ce7eed" xlink:to="loc_ago_MeasurementInputExitMultiplePriceToEarningsMember_019eb852-e0e8-72a8-8c92-0743b8e491a5" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb852-e0e8-7da1-9307-03ac3555032e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_srt_RangeAxis_019eb852-e0e8-7da1-9307-03ac3555032e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e0e8-7da1-9307-03ac3555032e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb852-e0e8-7da1-9307-03ac3555032e" xlink:to="loc_srt_RangeMember_019eb852-e0e8-7da1-9307-03ac3555032e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb852-e0e8-77d1-a8f0-f0f706ca4e03" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb852-e0e8-7da1-9307-03ac3555032e" xlink:to="loc_srt_RangeMember_019eb852-e0e8-77d1-a8f0-f0f706ca4e03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb852-e0e8-74d1-a404-4a7bb89f8f9e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e0e8-77d1-a8f0-f0f706ca4e03" xlink:to="loc_srt_MinimumMember_019eb852-e0e8-74d1-a404-4a7bb89f8f9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb852-e0e8-7662-ad82-0bb6ec6b2541" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e0e8-77d1-a8f0-f0f706ca4e03" xlink:to="loc_srt_MaximumMember_019eb852-e0e8-7662-ad82-0bb6ec6b2541" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_019eb852-e0e8-7a4b-99a2-bc92b70b5c9e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb852-e0e8-77d1-a8f0-f0f706ca4e03" xlink:to="loc_srt_WeightedAverageMember_019eb852-e0e8-7a4b-99a2-bc92b70b5c9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis_019eb852-e0e8-75c3-8ec5-b0caac2421c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_us-gaap_ValuationTechniqueAxis_019eb852-e0e8-75c3-8ec5-b0caac2421c8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-75c3-8ec5-b0caac2421c8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019eb852-e0e8-75c3-8ec5-b0caac2421c8" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-75c3-8ec5-b0caac2421c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-7a73-8488-bac6948a7a42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019eb852-e0e8-75c3-8ec5-b0caac2421c8" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-7a73-8488-bac6948a7a42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember_019eb852-e0e8-7861-b878-5b43cc1d8c0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-7a73-8488-bac6948a7a42" xlink:to="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember_019eb852-e0e8-7861-b878-5b43cc1d8c0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeApproachValuationTechniqueMember_019eb852-e0e8-7210-8d95-79d99047d6b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeApproachValuationTechniqueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-7a73-8488-bac6948a7a42" xlink:to="loc_us-gaap_IncomeApproachValuationTechniqueMember_019eb852-e0e8-7210-8d95-79d99047d6b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketApproachValuationTechniqueMember_019eb852-e0e8-7c3f-8689-9ca5803b18e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketApproachValuationTechniqueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019eb852-e0e8-7a73-8488-bac6948a7a42" xlink:to="loc_us-gaap_MarketApproachValuationTechniqueMember_019eb852-e0e8-7c3f-8689-9ca5803b18e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-74ac-9fd1-8d45e53caa11" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-74ac-9fd1-8d45e53caa11" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-74ac-9fd1-8d45e53caa11_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-74ac-9fd1-8d45e53caa11" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-74ac-9fd1-8d45e53caa11_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-70fa-9136-bd72ee0f5b54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb852-e0e8-74ac-9fd1-8d45e53caa11" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-70fa-9136-bd72ee0f5b54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019eb852-e0e8-7001-a6d4-0fc532f0638b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb852-e0e8-70fa-9136-bd72ee0f5b54" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019eb852-e0e8-7001-a6d4-0fc532f0638b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7baf-b537-d04930710d88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7baf-b537-d04930710d88" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7baf-b537-d04930710d88_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7baf-b537-d04930710d88" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7baf-b537-d04930710d88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb852-e0e8-7baf-b537-d04930710d88" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7b78-8f40-378670806a72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019eb852-e0e8-7b78-8f40-378670806a72" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-7d2c-904e-7f80aa1f9a59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb852-e0e8-7d2c-904e-7f80aa1f9a59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7cd6-b000-4da22329258c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019eb852-e0e8-7cd6-b000-4da22329258c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedLoanObligationsMember_019eb852-e0e8-7054-bab5-d0b7653dd7b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CollateralizedLoanObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:to="loc_us-gaap_CollateralizedLoanObligationsMember_019eb852-e0e8-7054-bab5-d0b7653dd7b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherAssetBackedSecuritiesMember_019eb852-e0e8-705b-ba1f-28a5b94d6f06" xlink:href="ago-20260630.xsd#ago_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb852-e0e8-7dc6-b0d7-8a0d7f1f022a" xlink:to="loc_ago_OtherAssetBackedSecuritiesMember_019eb852-e0e8-705b-ba1f-28a5b94d6f06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7b3c-9082-e717463b980f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019eb852-e0e8-731c-91b6-2137cc3d50c4" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7b3c-9082-e717463b980f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7b3c-9082-e717463b980f_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7b3c-9082-e717463b980f" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-7b3c-9082-e717463b980f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-75dd-b22c-07168e5e1d49" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019eb852-e0e8-7b3c-9082-e717463b980f" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-75dd-b22c-07168e5e1d49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-7a82-b015-89271fe39110" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019eb852-e0e8-75dd-b22c-07168e5e1d49" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019eb852-e0e8-7a82-b015-89271fe39110" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7db0-98ec-1dbf9ba64317" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019eb852-e0e8-7db0-98ec-1dbf9ba64317" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleMeasurementInput_019eb852-e0e8-74d9-bdd8-238aef34153d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleMeasurementInput_019eb852-e0e8-74d9-bdd8-238aef34153d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-70e0-ad5f-726f21987f09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TradingSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_TradingSecuritiesDebt_019eb852-e0e8-70e0-ad5f-726f21987f09" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesTradingMeasurementInput_019eb852-e0e8-7f06-8ba9-1faf1238c833" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesTradingMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_DebtSecuritiesTradingMeasurementInput_019eb852-e0e8-7f06-8ba9-1faf1238c833" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FundsHeldUnderReinsuranceAgreementsAsset_019eb852-e0e8-7b0f-a69a-72138aebd7e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FundsHeldUnderReinsuranceAgreementsAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_FundsHeldUnderReinsuranceAgreementsAsset_019eb852-e0e8-7b0f-a69a-72138aebd7e6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FundsWithheldMeasurementInput_019eb852-e0e8-7398-ac55-d3e841d27ba8" xlink:href="ago-20260630.xsd#ago_FundsWithheldMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_ago_FundsWithheldMeasurementInput_019eb852-e0e8-7398-ac55-d3e841d27ba8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019eb852-e0e8-766c-8dd1-6333d45daea5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019eb852-e0e8-766c-8dd1-6333d45daea5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_AssetsFairValueMeasurementInput_019eb852-e0e8-7f30-9532-44ff6a5dbd49" xlink:href="ago-20260630.xsd#ago_AssetsFairValueMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_ago_AssetsFairValueMeasurementInput_019eb852-e0e8-7f30-9532-44ff6a5dbd49" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019eb852-e0e8-7506-b196-c5e4d15d8f4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019eb852-e0e8-7506-b196-c5e4d15d8f4b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiMeasurementInput_019eb852-e0e8-72d2-be39-c8eb00179b25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_EquitySecuritiesFvNiMeasurementInput_019eb852-e0e8-72d2-be39-c8eb00179b25" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_019eb852-e0e8-7004-8507-2953a31ddae5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_019eb852-e0e8-7004-8507-2953a31ddae5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_OtherAssetsFairValueDisclosureMeasurementInput_019eb852-e0e8-787e-9425-242249230f29" xlink:href="ago-20260630.xsd#ago_OtherAssetsFairValueDisclosureMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_ago_OtherAssetsFairValueDisclosureMeasurementInput_019eb852-e0e8-787e-9425-242249230f29" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019eb852-e0e8-7d7f-88ec-1d58effb9027" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019eb852-e0e8-7d7f-88ec-1d58effb9027" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetLiabilityNetMeasurementInput_019eb852-e0e8-74fb-bddb-68280384292a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetLiabilityNetMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_DerivativeAssetLiabilityNetMeasurementInput_019eb852-e0e8-74fb-bddb-68280384292a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019eb852-e0e8-763f-8e7b-96cc1461ea4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019eb852-e0e8-763f-8e7b-96cc1461ea4a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_LiabilitiesFairValueMeasurementInput_019eb852-e0e8-7b3b-b681-ce6a9511b0c0" xlink:href="ago-20260630.xsd#ago_LiabilitiesFairValueMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019eb852-e0e8-7aa8-9ce8-f8ff5a9ac6d2" xlink:to="loc_ago_LiabilitiesFairValueMeasurementInput_019eb852-e0e8-7b3b-b681-ce6a9511b0c0" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/FairValueMeasurementFairValueofFinancialInstrumentsNotCarriedatFairValueDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#FairValueMeasurementFairValueofFinancialInstrumentsNotCarriedatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/FairValueMeasurementFairValueofFinancialInstrumentsNotCarriedatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019eb852-e0e8-7cb6-a9a9-718bf49fa804" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019eb852-e0e8-7cb6-a9a9-718bf49fa804" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019eb852-e0e8-72ee-8330-33449aeb23a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019eb852-e0e8-7cb6-a9a9-718bf49fa804" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019eb852-e0e8-72ee-8330-33449aeb23a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019eb852-e0e8-72ee-8330-33449aeb23a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019eb852-e0e8-72ee-8330-33449aeb23a1" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019eb852-e0e8-72ee-8330-33449aeb23a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019eb852-e0e8-74ac-89af-b871a114e5dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019eb852-e0e8-72ee-8330-33449aeb23a1" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019eb852-e0e8-74ac-89af-b871a114e5dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019eb852-e0e8-7f3b-82fc-f2627c87a2eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019eb852-e0e8-74ac-89af-b871a114e5dc" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019eb852-e0e8-7f3b-82fc-f2627c87a2eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019eb852-e0e8-7bbb-b4c9-6b3bc9473068" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019eb852-e0e8-7f3b-82fc-f2627c87a2eb" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019eb852-e0e8-7bbb-b4c9-6b3bc9473068" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019eb852-e0e8-77c9-bdf2-826456ae72b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019eb852-e0e8-7f3b-82fc-f2627c87a2eb" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019eb852-e0e8-77c9-bdf2-826456ae72b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019eb852-e0e8-7ee6-8d37-b037539fa319" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_us-gaap_OtherAssets_019eb852-e0e8-7ee6-8d37-b037539fa319" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyInsuranceContractsNetValue_019eb852-e0e8-7cbb-85e2-67b0749e1bec" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyInsuranceContractsNetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_ago_FinancialGuarantyInsuranceContractsNetValue_019eb852-e0e8-7cbb-85e2-67b0749e1bec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderFunds_019eb852-e0e8-74e9-8e17-d86f8285a922" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderFunds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_us-gaap_PolicyholderFunds_019eb852-e0e8-74e9-8e17-d86f8285a922" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019eb852-e0e8-7f2e-bd75-227ce402d32e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_us-gaap_LongTermDebt_019eb852-e0e8-7f2e-bd75-227ce402d32e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_FinancialGuarantyOfVariableInterestEntitiesLiabilityHeld_019eb852-e0e8-78b1-8dfa-060c751a343e" xlink:href="ago-20260630.xsd#ago_FinancialGuarantyOfVariableInterestEntitiesLiabilityHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_ago_FinancialGuarantyOfVariableInterestEntitiesLiabilityHeld_019eb852-e0e8-78b1-8dfa-060c751a343e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019eb852-e0e8-719a-b79f-1a158ac671b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019eb852-e0e8-7ec3-abbf-56d24b753365" xlink:to="loc_us-gaap_OtherLiabilities_019eb852-e0e8-719a-b79f-1a158ac671b6" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/IncomeTaxesDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#IncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/IncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ago_IncomeTaxesLineItems_019eb852-e0e8-7d46-b053-83d40ea8522b" xlink:href="ago-20260630.xsd#ago_IncomeTaxesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_IncomeTaxesTable_019eb852-e0e8-7586-bece-96a60b69e0e1" xlink:href="ago-20260630.xsd#ago_IncomeTaxesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ago_IncomeTaxesLineItems_019eb852-e0e8-7d46-b053-83d40ea8522b" xlink:to="loc_ago_IncomeTaxesTable_019eb852-e0e8-7586-bece-96a60b69e0e1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_019eb852-e0e8-7a75-9fa8-89a647dbc618" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ago_IncomeTaxesTable_019eb852-e0e8-7586-bece-96a60b69e0e1" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_019eb852-e0e8-7a75-9fa8-89a647dbc618" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7a75-9fa8-89a647dbc618_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019eb852-e0e8-7a75-9fa8-89a647dbc618" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7a75-9fa8-89a647dbc618_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7614-908f-48cabf1ee84d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019eb852-e0e8-7a75-9fa8-89a647dbc618" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7614-908f-48cabf1ee84d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_GB_019eb852-e0e8-74f7-92b0-5f7bae7a4be9" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_GB"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7614-908f-48cabf1ee84d" xlink:to="loc_country_GB_019eb852-e0e8-74f7-92b0-5f7bae7a4be9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_BM_019eb852-e0e8-7469-a951-7fe1197924ec" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_BM"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7614-908f-48cabf1ee84d" xlink:to="loc_country_BM_019eb852-e0e8-7469-a951-7fe1197924ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb852-e0e8-78c4-b088-fc7dd7683cf6" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7614-908f-48cabf1ee84d" xlink:to="loc_country_US_019eb852-e0e8-78c4-b088-fc7dd7683cf6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_FR_019eb852-e0e8-70d2-a6c1-4be45b08220c" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_FR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019eb852-e0e8-7614-908f-48cabf1ee84d" xlink:to="loc_country_FR_019eb852-e0e8-70d2-a6c1-4be45b08220c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_EffectiveIncomeTaxRateReconciliationGlobalMinimumTaxRatePercent_019eb852-e0e8-71b5-8414-98a6c65c0880" xlink:href="ago-20260630.xsd#ago_EffectiveIncomeTaxRateReconciliationGlobalMinimumTaxRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_IncomeTaxesLineItems_019eb852-e0e8-7d46-b053-83d40ea8522b" xlink:to="loc_ago_EffectiveIncomeTaxRateReconciliationGlobalMinimumTaxRatePercent_019eb852-e0e8-71b5-8414-98a6c65c0880" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019eb852-e0e8-7555-8e80-942f57ae6838" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_IncomeTaxesLineItems_019eb852-e0e8-7d46-b053-83d40ea8522b" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019eb852-e0e8-7555-8e80-942f57ae6838" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_EffectiveIncomeTaxRateReconciliationGlobalMinimumTaxAmount_019eb852-e0e8-7fc0-8c05-47bb877dbad3" xlink:href="ago-20260630.xsd#ago_EffectiveIncomeTaxRateReconciliationGlobalMinimumTaxAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_IncomeTaxesLineItems_019eb852-e0e8-7d46-b053-83d40ea8522b" xlink:to="loc_ago_EffectiveIncomeTaxRateReconciliationGlobalMinimumTaxAmount_019eb852-e0e8-7fc0-8c05-47bb877dbad3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019eb852-e0e8-757d-8e59-4306aa35b55e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ago_IncomeTaxesLineItems_019eb852-e0e8-7d46-b053-83d40ea8522b" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019eb852-e0e8-757d-8e59-4306aa35b55e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ShareholdersEquityChangesinAOCIbyComponentDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ShareholdersEquityChangesinAOCIbyComponentDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ShareholdersEquityChangesinAOCIbyComponentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_019eb852-e0e8-7596-ae77-f2a018aa59c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_019eb852-e0e8-7596-ae77-f2a018aa59c6" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7b18-bc5d-518555a22c17_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7b18-bc5d-518555a22c17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7603-abc4-fad1561cb571" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7603-abc4-fad1561cb571" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7603-abc4-fad1561cb571" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParentMember_019eb852-e0e8-7134-89c0-1ffbdbaf901f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParentMember_019eb852-e0e8-7134-89c0-1ffbdbaf901f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParentMember_019eb852-e0e8-7525-bd70-e8147db741e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParentMember_019eb852-e0e8-7525-bd70-e8147db741e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossFinancialLiabilityFairValueOptionAttributableToParentMember_019eb852-e0e8-767f-953b-485cee5198ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedGainLossFinancialLiabilityFairValueOptionAttributableToParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AccumulatedGainLossFinancialLiabilityFairValueOptionAttributableToParentMember_019eb852-e0e8-767f-953b-485cee5198ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociLiabilityForFuturePolicyBenefitParentMember_019eb852-e0e8-72ef-be36-56ada487a518" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociLiabilityForFuturePolicyBenefitParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AociLiabilityForFuturePolicyBenefitParentMember_019eb852-e0e8-72ef-be36-56ada487a518" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019eb852-e0e8-7652-a9b0-020718f6ed4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019eb852-e0e8-7652-a9b0-020718f6ed4a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019eb852-e0e8-702e-9796-51e97e6323a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019eb852-e0e8-702e-9796-51e97e6323a6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019eb852-e0e8-7c47-8bfd-bda06a4bc454" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019eb852-e0e8-7c47-8bfd-bda06a4bc454" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_019eb852-e0e8-7596-ae77-f2a018aa59c6" xlink:to="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-e0e8-761f-8b9f-b92128a13872" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-e0e8-761f-8b9f-b92128a13872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_019eb852-e0e8-7140-8480-3f2ea78b9990" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_019eb852-e0e8-7140-8480-3f2ea78b9990" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_019eb852-e0e8-7ffe-b96a-9bc99e1341b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_019eb852-e0e8-7ffe-b96a-9bc99e1341b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019eb852-e0e8-7edc-af61-00080e04ce6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019eb852-e0e8-7edc-af61-00080e04ce6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_019eb852-e0e8-7452-84a8-9ac8065e25db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_019eb852-e0e8-7452-84a8-9ac8065e25db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb852-e0e8-747c-806a-1bab9a556482" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb852-e0e8-747c-806a-1bab9a556482" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-e0e8-73e0-909f-a85b78306714" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ShareholdersEquityChangesinAOCIbyComponentDetails_1" xlink:type="simple" xlink:href="ago-20260630.xsd#ShareholdersEquityChangesinAOCIbyComponentDetails_1"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ShareholdersEquityChangesinAOCIbyComponentDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_019eb852-e0e8-7596-ae77-f2a018aa59c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_019eb852-e0e8-7596-ae77-f2a018aa59c6" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_019eb852-e0e8-71cd-be1b-f1140ba6750a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7b18-bc5d-518555a22c17_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7b18-bc5d-518555a22c17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7603-abc4-fad1561cb571" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7b18-bc5d-518555a22c17" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7603-abc4-fad1561cb571" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7603-abc4-fad1561cb571" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParentMember_019eb852-e0e8-7134-89c0-1ffbdbaf901f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParentMember_019eb852-e0e8-7134-89c0-1ffbdbaf901f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParentMember_019eb852-e0e8-7525-bd70-e8147db741e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParentMember_019eb852-e0e8-7525-bd70-e8147db741e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossFinancialLiabilityFairValueOptionAttributableToParentMember_019eb852-e0e8-767f-953b-485cee5198ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedGainLossFinancialLiabilityFairValueOptionAttributableToParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AccumulatedGainLossFinancialLiabilityFairValueOptionAttributableToParentMember_019eb852-e0e8-767f-953b-485cee5198ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociLiabilityForFuturePolicyBenefitParentMember_019eb852-e0e8-72ef-be36-56ada487a518" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociLiabilityForFuturePolicyBenefitParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AociLiabilityForFuturePolicyBenefitParentMember_019eb852-e0e8-72ef-be36-56ada487a518" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019eb852-e0e8-7652-a9b0-020718f6ed4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019eb852-e0e8-7652-a9b0-020718f6ed4a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019eb852-e0e8-702e-9796-51e97e6323a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb852-e0e8-7d87-b02a-08ea81718be2" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019eb852-e0e8-702e-9796-51e97e6323a6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_019eb852-e0e8-7596-ae77-f2a018aa59c6" xlink:to="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-e0e8-761f-8b9f-b92128a13872" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-e0e8-761f-8b9f-b92128a13872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_019eb852-e0e8-7140-8480-3f2ea78b9990" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_019eb852-e0e8-7140-8480-3f2ea78b9990" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_019eb852-e0e8-7ffe-b96a-9bc99e1341b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_019eb852-e0e8-7ffe-b96a-9bc99e1341b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019eb852-e0e8-7edc-af61-00080e04ce6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTaxAbstract_019eb852-e0e8-7f21-9a0e-59008a082a02" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019eb852-e0e8-7edc-af61-00080e04ce6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_019eb852-e0e8-7452-84a8-9ac8065e25db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_019eb852-e0e8-7452-84a8-9ac8065e25db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb852-e0e8-747c-806a-1bab9a556482" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIIncludingPortionAttributableToNoncontrollingInterestAbstract_019eb852-e0e8-7cfc-bd8a-f79a44a312d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb852-e0e8-747c-806a-1bab9a556482" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019eb852-e0e8-73e0-909f-a85b78306714" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ShareholdersEquitySharesRepurchasedDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ShareholdersEquitySharesRepurchasedDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ShareholdersEquitySharesRepurchasedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7f89-a836-2216403ba01b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityClassOfTreasuryStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77c2-8113-10ceac3c5bd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfTreasuryStockTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7f89-a836-2216403ba01b" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77c2-8113-10ceac3c5bd0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7d46-8cfe-53dc774a72d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77c2-8113-10ceac3c5bd0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7d46-8cfe-53dc774a72d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7d46-8cfe-53dc774a72d1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7d46-8cfe-53dc774a72d1" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7d46-8cfe-53dc774a72d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7aa1-ae56-fb44c15d816d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7d46-8cfe-53dc774a72d1" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7aa1-ae56-fb44c15d816d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019eb852-e0e8-7659-af32-7efe28be7939" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7aa1-ae56-fb44c15d816d" xlink:to="loc_us-gaap_CommonStockMember_019eb852-e0e8-7659-af32-7efe28be7939" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-78b1-8a04-4a9365ee9c71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77c2-8113-10ceac3c5bd0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-78b1-8a04-4a9365ee9c71" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-78b1-8a04-4a9365ee9c71_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-78b1-8a04-4a9365ee9c71" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-78b1-8a04-4a9365ee9c71_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-70a2-ac93-3792b886a157" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-78b1-8a04-4a9365ee9c71" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-70a2-ac93-3792b886a157" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019eb852-e0e8-7818-b5eb-b36643047552" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-70a2-ac93-3792b886a157" xlink:to="loc_us-gaap_SubsequentEventMember_019eb852-e0e8-7818-b5eb-b36643047552" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019eb852-e0e8-7058-a2ac-70a5919eeac3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7f89-a836-2216403ba01b" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019eb852-e0e8-7058-a2ac-70a5919eeac3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019eb852-e0e8-7d4f-a721-2a3c4f01e9aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7f89-a836-2216403ba01b" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019eb852-e0e8-7d4f-a721-2a3c4f01e9aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019eb852-e0e8-7d64-9c80-3206f7cf75c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7f89-a836-2216403ba01b" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019eb852-e0e8-7d64-9c80-3206f7cf75c4" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.assuredguaranty.com/role/ShareholdersEquityAdditionalInformationDetails" xlink:type="simple" xlink:href="ago-20260630.xsd#ShareholdersEquityAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.assuredguaranty.com/role/ShareholdersEquityAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7582-a901-6c4098da1a2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityClassOfTreasuryStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77e2-bea2-8213b417f974" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfTreasuryStockTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7582-a901-6c4098da1a2d" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77e2-bea2-8213b417f974" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7960-a166-28a04ed21b07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77e2-bea2-8213b417f974" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7960-a166-28a04ed21b07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7960-a166-28a04ed21b07_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7960-a166-28a04ed21b07" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-7960-a166-28a04ed21b07_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-750e-99a8-18a7747f12af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb852-e0e8-7960-a166-28a04ed21b07" xlink:to="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-750e-99a8-18a7747f12af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019eb852-e0e8-7a06-acf0-954f4a4dcb21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb852-e0e8-750e-99a8-18a7747f12af" xlink:to="loc_us-gaap_CommonStockMember_019eb852-e0e8-7a06-acf0-954f4a4dcb21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-76fa-a60e-b815a8eb9c03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_019eb852-e0e8-77e2-bea2-8213b417f974" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-76fa-a60e-b815a8eb9c03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-76fa-a60e-b815a8eb9c03_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-76fa-a60e-b815a8eb9c03" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-76fa-a60e-b815a8eb9c03_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-724d-99b2-7e2733eee937" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019eb852-e0e8-76fa-a60e-b815a8eb9c03" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-724d-99b2-7e2733eee937" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019eb852-e0e8-7943-a653-159efeb81df7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019eb852-e0e8-724d-99b2-7e2733eee937" xlink:to="loc_us-gaap_SubsequentEventMember_019eb852-e0e8-7943-a653-159efeb81df7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ago_ShareRepurchaseProgramAdditionalAmountAuthorized_019eb852-e0e8-7c33-afc1-2c02765df9a6" xlink:href="ago-20260630.xsd#ago_ShareRepurchaseProgramAdditionalAmountAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_019eb852-e0e8-7582-a901-6c4098da1a2d" xlink:to="loc_ago_ShareRepurchaseProgramAdditionalAmountAuthorized_019eb852-e0e8-7c33-afc1-2c02765df9a6" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
