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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019dd9a5-d708-7330-ba2b-e6fd122bf88a,g:e2f8c6dc-83ae-458c-9e68-5ae45984b429-->
<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.tradeweb.com/role/Cover" xlink:type="simple" xlink:href="tw-20260630.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019dd9a5-d910-727f-a784-52c62ca81ad0" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntitiesTable_019dd9a5-d910-727f-a784-52c62ca81ad0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-73c4-b8ef-ebd179cca6c6" 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_019dd9a5-d910-727f-a784-52c62ca81ad0" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-73c4-b8ef-ebd179cca6c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-73c4-b8ef-ebd179cca6c6_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_019dd9a5-d910-73c4-b8ef-ebd179cca6c6" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-73c4-b8ef-ebd179cca6c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-717b-a477-008a1b5c3782" 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_019dd9a5-d910-73c4-b8ef-ebd179cca6c6" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-717b-a477-008a1b5c3782" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7a60-b026-1ce4b117c7ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-717b-a477-008a1b5c3782" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7a60-b026-1ce4b117c7ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7c50-83c6-23939865e2e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-717b-a477-008a1b5c3782" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7c50-83c6-23939865e2e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7e1f-8697-91b947ebefce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-717b-a477-008a1b5c3782" xlink:to="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7e1f-8697-91b947ebefce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CommonClassDMember_019dd9a5-d910-71bf-af86-f62aec739e29" xlink:href="tw-20260630.xsd#tw_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-717b-a477-008a1b5c3782" xlink:to="loc_tw_CommonClassDMember_019dd9a5-d910-71bf-af86-f62aec739e29" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019dd9a5-d910-7819-a754-48a88a477aec" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_DocumentType_019dd9a5-d910-7819-a754-48a88a477aec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019dd9a5-d910-7569-9f4b-c5bf7d02b261" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_DocumentQuarterlyReport_019dd9a5-d910-7569-9f4b-c5bf7d02b261" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019dd9a5-d910-71c6-b441-2dbd0c3172a9" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_DocumentPeriodEndDate_019dd9a5-d910-71c6-b441-2dbd0c3172a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019dd9a5-d910-7f91-a455-c5b2a87020eb" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_DocumentTransitionReport_019dd9a5-d910-7f91-a455-c5b2a87020eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019dd9a5-d910-748d-afce-afc4a8142b0c" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityFileNumber_019dd9a5-d910-748d-afce-afc4a8142b0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019dd9a5-d910-7523-acd4-3dc30a125e39" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityRegistrantName_019dd9a5-d910-7523-acd4-3dc30a125e39" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019dd9a5-d910-76f2-84a5-3e541b1bf76c" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019dd9a5-d910-76f2-84a5-3e541b1bf76c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019dd9a5-d910-7f7f-8770-211e08ed72ab" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityTaxIdentificationNumber_019dd9a5-d910-7f7f-8770-211e08ed72ab" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019dd9a5-d910-7aa1-bef0-9cd209c6b0a5" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityAddressAddressLine1_019dd9a5-d910-7aa1-bef0-9cd209c6b0a5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019dd9a5-d910-711a-b1cc-3b5aba142316" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityAddressCityOrTown_019dd9a5-d910-711a-b1cc-3b5aba142316" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019dd9a5-d910-7085-a528-f6734a51a3c4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityAddressStateOrProvince_019dd9a5-d910-7085-a528-f6734a51a3c4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019dd9a5-d910-75b6-875b-7ea473bee9c5" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityAddressPostalZipCode_019dd9a5-d910-75b6-875b-7ea473bee9c5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019dd9a5-d910-7251-8b9d-60f0da20935e" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_CityAreaCode_019dd9a5-d910-7251-8b9d-60f0da20935e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019dd9a5-d910-7194-8685-124628da578a" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_LocalPhoneNumber_019dd9a5-d910-7194-8685-124628da578a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019dd9a5-d910-78bf-9366-2df08e4e8ce4" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_Security12bTitle_019dd9a5-d910-78bf-9366-2df08e4e8ce4" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019dd9a5-d910-77dd-b062-b47cc884c357" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_TradingSymbol_019dd9a5-d910-77dd-b062-b47cc884c357" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019dd9a5-d910-70c8-bbaf-bae59e015dc8" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_SecurityExchangeName_019dd9a5-d910-70c8-bbaf-bae59e015dc8" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019dd9a5-d910-7933-8010-ad35866139de" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityCurrentReportingStatus_019dd9a5-d910-7933-8010-ad35866139de" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019dd9a5-d910-7ddf-bfee-1aeb20be8f7b" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityInteractiveDataCurrent_019dd9a5-d910-7ddf-bfee-1aeb20be8f7b" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019dd9a5-d910-7227-80a8-6e8e0149aa97" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityFilerCategory_019dd9a5-d910-7227-80a8-6e8e0149aa97" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019dd9a5-d910-7842-94b8-a3cc8f68f482" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntitySmallBusiness_019dd9a5-d910-7842-94b8-a3cc8f68f482" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019dd9a5-d910-7ef1-92fa-cb0e9485b69d" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityEmergingGrowthCompany_019dd9a5-d910-7ef1-92fa-cb0e9485b69d" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019dd9a5-d910-77d8-9c57-1ff7d4863373" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityShellCompany_019dd9a5-d910-77d8-9c57-1ff7d4863373" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019dd9a5-d910-7849-87e5-84fd8f84eea8" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019dd9a5-d910-7849-87e5-84fd8f84eea8" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019dd9a5-d910-7e7e-a8b4-50b495570a7f" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_EntityCentralIndexKey_019dd9a5-d910-7e7e-a8b4-50b495570a7f" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019dd9a5-d910-7bd7-b581-ea1b7d6b3a22" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_CurrentFiscalYearEndDate_019dd9a5-d910-7bd7-b581-ea1b7d6b3a22" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019dd9a5-d910-73a9-96ef-4d2b582ebce8" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_DocumentFiscalYearFocus_019dd9a5-d910-73a9-96ef-4d2b582ebce8" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019dd9a5-d910-7fd6-9fcc-a5ff1ec32f05" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019dd9a5-d910-7fd6-9fcc-a5ff1ec32f05" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019dd9a5-d910-772c-8870-33d4c8445137" 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_019dd9a5-d910-7d21-8716-25c3dac7b6ed" xlink:to="loc_dei_AmendmentFlag_019dd9a5-d910-772c-8870-33d4c8445137" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofFinancialCondition" xlink:type="simple" xlink:href="tw-20260630.xsd#CondensedConsolidatedStatementsofFinancialCondition"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofFinancialCondition" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019dd9a5-d910-76aa-9a86-dfed634b466c" 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_019dd9a5-d910-7754-b2e0-02098a799e11" 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_019dd9a5-d910-76aa-9a86-dfed634b466c" xlink:to="loc_us-gaap_StatementTable_019dd9a5-d910-7754-b2e0-02098a799e11" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7809-86c9-7b8cb049afbd" 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_us-gaap_StatementTable_019dd9a5-d910-7754-b2e0-02098a799e11" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7809-86c9-7b8cb049afbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7809-86c9-7b8cb049afbd_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_019dd9a5-d910-7809-86c9-7b8cb049afbd" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7809-86c9-7b8cb049afbd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7211-a26a-db2c435e9baf" 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_019dd9a5-d910-7809-86c9-7b8cb049afbd" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7211-a26a-db2c435e9baf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7370-af81-8aac7a80896d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7211-a26a-db2c435e9baf" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7370-af81-8aac7a80896d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7fd8-8188-28470f97c52f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7211-a26a-db2c435e9baf" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7fd8-8188-28470f97c52f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7518-a926-63630d72bd8a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7211-a26a-db2c435e9baf" xlink:to="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7518-a926-63630d72bd8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CommonClassDMember_019dd9a5-d910-70e2-8e6f-1e137fff0dca" xlink:href="tw-20260630.xsd#tw_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7211-a26a-db2c435e9baf" xlink:to="loc_tw_CommonClassDMember_019dd9a5-d910-70e2-8e6f-1e137fff0dca" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-76aa-9a86-dfed634b466c" xlink:to="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019dd9a5-d910-7a2b-b4da-228b1fac807f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019dd9a5-d910-7a2b-b4da-228b1fac807f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_019dd9a5-d910-7417-bb1f-27a62f430e78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_RestrictedCash_019dd9a5-d910-7417-bb1f-27a62f430e78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations_019dd9a5-d910-7aff-8e70-5e8a623d0f5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations_019dd9a5-d910-7aff-8e70-5e8a623d0f5c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsWithClearingOrganizationsAndOthersSecurities_019dd9a5-d910-7176-9b11-cc40b97bbbab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepositsWithClearingOrganizationsAndOthersSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_DepositsWithClearingOrganizationsAndOthersSecurities_019dd9a5-d910-7176-9b11-cc40b97bbbab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance_019dd9a5-d910-749a-bf21-78063968f041" xlink:href="tw-20260630.xsd#tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance_019dd9a5-d910-749a-bf21-78063968f041" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019dd9a5-d910-749d-9273-b9672f03bdd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019dd9a5-d910-749d-9273-b9672f03bdd9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019dd9a5-d910-7c79-a5d1-9a90398fd00c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019dd9a5-d910-7c79-a5d1-9a90398fd00c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_IntangibleAsseFiniteLivedSoftwareDevelopmentCostsNet_019dd9a5-d910-7bc5-aa4a-852d8acf03e1" xlink:href="tw-20260630.xsd#tw_IntangibleAsseFiniteLivedSoftwareDevelopmentCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_tw_IntangibleAsseFiniteLivedSoftwareDevelopmentCostsNet_019dd9a5-d910-7bc5-aa4a-852d8acf03e1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019dd9a5-d910-7253-8646-aedb1c089873" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_Goodwill_019dd9a5-d910-7253-8646-aedb1c089873" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsNet_019dd9a5-d910-76ae-a53f-c9707d9e9acb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_OtherIntangibleAssetsNet_019dd9a5-d910-76ae-a53f-c9707d9e9acb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_019dd9a5-d910-7866-af90-522986c31437" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_OtherReceivables_019dd9a5-d910-7866-af90-522986c31437" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019dd9a5-d910-78da-9d39-67fecb9ebaba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019dd9a5-d910-78da-9d39-67fecb9ebaba" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_019dd9a5-d910-789f-b9b6-1638a8a6fc9d" 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_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_Investments_019dd9a5-d910-789f-b9b6-1638a8a6fc9d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019dd9a5-d910-79f0-a286-55febc0cb219" 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_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_OtherAssets_019dd9a5-d910-79f0-a286-55febc0cb219" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019dd9a5-d910-7306-8f5e-59777328b9d1" 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_AssetsAbstract_019dd9a5-d910-7c43-8cc0-5bce6700925c" xlink:to="loc_us-gaap_Assets_019dd9a5-d910-7306-8f5e-59777328b9d1" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019dd9a5-d910-7e90-96af-eda0a17838df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-76aa-9a86-dfed634b466c" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019dd9a5-d910-7e90-96af-eda0a17838df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019dd9a5-d910-7e90-96af-eda0a17838df" xlink:to="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_PayablesToBrokerDealersAndClearingOrganizations_019dd9a5-d910-7ab8-be72-04e3d2528fa2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_PayablesToBrokerDealersAndClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_srt_PayablesToBrokerDealersAndClearingOrganizations_019dd9a5-d910-7ab8-be72-04e3d2528fa2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent_019dd9a5-d910-74ab-bb93-f878124a37be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent_019dd9a5-d910-74ab-bb93-f878124a37be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019dd9a5-d910-79ed-bce1-d6c31b990480" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019dd9a5-d910-79ed-bce1-d6c31b990480" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019dd9a5-d910-7264-b71e-5fbc37f33192" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019dd9a5-d910-7264-b71e-5fbc37f33192" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019dd9a5-d910-795c-aef5-0d49740b74b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_OperatingLeaseLiability_019dd9a5-d910-795c-aef5-0d49740b74b9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019dd9a5-d910-7f9c-9353-9b83bc9b8f95" 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_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_OtherLiabilities_019dd9a5-d910-7f9c-9353-9b83bc9b8f95" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019dd9a5-d910-765d-8579-cb8df9fb040f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019dd9a5-d910-765d-8579-cb8df9fb040f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TaxReceivableAgreementLiability_019dd9a5-d910-7112-890a-0d3213f169f7" xlink:href="tw-20260630.xsd#tw_TaxReceivableAgreementLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_tw_TaxReceivableAgreementLiability_019dd9a5-d910-7112-890a-0d3213f169f7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019dd9a5-d910-724c-824b-66af2843d236" 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_LiabilitiesAbstract_019dd9a5-d910-73f1-a399-76c60b1083b2" xlink:to="loc_us-gaap_Liabilities_019dd9a5-d910-724c-824b-66af2843d236" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019dd9a5-d910-73f4-a87a-6065d083ba3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019dd9a5-d910-7e90-96af-eda0a17838df" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019dd9a5-d910-73f4-a87a-6065d083ba3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MembersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019dd9a5-d910-7e90-96af-eda0a17838df" xlink:to="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_019dd9a5-d910-79b7-9480-7b063cd8c18a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_PreferredStockValue_019dd9a5-d910-79b7-9480-7b063cd8c18a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019dd9a5-d910-7865-b913-7e595b99424c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_CommonStockValue_019dd9a5-d910-7865-b913-7e595b99424c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019dd9a5-d910-7d7b-a185-569f4eb3787e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019dd9a5-d910-7d7b-a185-569f4eb3787e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019dd9a5-d910-7cad-b87b-15031d89b9b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019dd9a5-d910-7cad-b87b-15031d89b9b2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019dd9a5-d910-7d7a-adeb-1980b122bdaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019dd9a5-d910-7d7a-adeb-1980b122bdaa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019dd9a5-d910-7c33-9142-3fc40496bed8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_StockholdersEquity_019dd9a5-d910-7c33-9142-3fc40496bed8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_019dd9a5-d910-7a09-97aa-91fbef0be1fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_MinorityInterest_019dd9a5-d910-7a09-97aa-91fbef0be1fd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019dd9a5-d910-74c5-809e-874aaf7fa012" 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_MembersEquityAbstract_019dd9a5-d910-7d38-8101-affa4e960b92" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019dd9a5-d910-74c5-809e-874aaf7fa012" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019dd9a5-d910-727b-8bef-f97ab2451d55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019dd9a5-d910-7e90-96af-eda0a17838df" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019dd9a5-d910-727b-8bef-f97ab2451d55" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofFinancialConditionParenthetical" xlink:type="simple" xlink:href="tw-20260630.xsd#CondensedConsolidatedStatementsofFinancialConditionParenthetical"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofFinancialConditionParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" 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_019dd9a5-d910-7439-9ea3-ebe4a124754d" 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_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_StatementTable_019dd9a5-d910-7439-9ea3-ebe4a124754d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7457-b900-79bdc5a56317" 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_us-gaap_StatementTable_019dd9a5-d910-7439-9ea3-ebe4a124754d" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7457-b900-79bdc5a56317" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7457-b900-79bdc5a56317_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_019dd9a5-d910-7457-b900-79bdc5a56317" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7457-b900-79bdc5a56317_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-72aa-a9d5-8f69df872b24" 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_019dd9a5-d910-7457-b900-79bdc5a56317" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-72aa-a9d5-8f69df872b24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7d0d-9078-7f02fba229ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-72aa-a9d5-8f69df872b24" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7d0d-9078-7f02fba229ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7cdc-bc9f-aacf3ce95844" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-72aa-a9d5-8f69df872b24" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7cdc-bc9f-aacf3ce95844" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7921-8d48-1f7f65ac23e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-72aa-a9d5-8f69df872b24" xlink:to="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7921-8d48-1f7f65ac23e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CommonClassDMember_019dd9a5-d910-7916-a74b-cd87c334a266" xlink:href="tw-20260630.xsd#tw_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-72aa-a9d5-8f69df872b24" xlink:to="loc_tw_CommonClassDMember_019dd9a5-d910-7916-a74b-cd87c334a266" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d910-7a5c-962a-1baf5be36836" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d910-7a5c-962a-1baf5be36836" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019dd9a5-d910-741f-9042-b5061696766f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019dd9a5-d910-741f-9042-b5061696766f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_019dd9a5-d910-7d77-9d72-7874bb1edb04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_019dd9a5-d910-7d77-9d72-7874bb1edb04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019dd9a5-d910-7024-8cb4-aef072a19ad1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019dd9a5-d910-7024-8cb4-aef072a19ad1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019dd9a5-d910-7ba5-bed3-b27c3d2d2931" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019dd9a5-d910-7ba5-bed3-b27c3d2d2931" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019dd9a5-d910-7f22-87ad-08b888148f3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019dd9a5-d910-7f22-87ad-08b888148f3b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019dd9a5-d910-705f-8788-1d2ba6cd8c2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019dd9a5-d910-705f-8788-1d2ba6cd8c2f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019dd9a5-d910-7308-b1dd-ed28fe0307e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_CommonStockSharesIssued_019dd9a5-d910-7308-b1dd-ed28fe0307e4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019dd9a5-d910-72a0-950b-125fdb356ebe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-778c-9157-154cda38a370" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019dd9a5-d910-72a0-950b-125fdb356ebe" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="tw-20260630.xsd#CondensedConsolidatedStatementsofIncome"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" 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_019dd9a5-d910-7be2-bfa3-4765241fed08" 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_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_StatementTable_019dd9a5-d910-7be2-bfa3-4765241fed08" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019dd9a5-d910-7572-87ae-9225591ca4d5" 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_StatementTable_019dd9a5-d910-7be2-bfa3-4765241fed08" xlink:to="loc_srt_ProductOrServiceAxis_019dd9a5-d910-7572-87ae-9225591ca4d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7572-87ae-9225591ca4d5_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_019dd9a5-d910-7572-87ae-9225591ca4d5" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7572-87ae-9225591ca4d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-701f-a23f-63ec69ed238e" 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_019dd9a5-d910-7572-87ae-9225591ca4d5" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-701f-a23f-63ec69ed238e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TransactionFeeRevenueMember_019dd9a5-d910-7c89-94dd-a83a559d0a93" xlink:href="tw-20260630.xsd#tw_TransactionFeeRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-701f-a23f-63ec69ed238e" xlink:to="loc_tw_TransactionFeeRevenueMember_019dd9a5-d910-7c89-94dd-a83a559d0a93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_SubscriptionFeeRevenueMember_019dd9a5-d910-70ad-bfda-53df8be8f6d9" xlink:href="tw-20260630.xsd#tw_SubscriptionFeeRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-701f-a23f-63ec69ed238e" xlink:to="loc_tw_SubscriptionFeeRevenueMember_019dd9a5-d910-70ad-bfda-53df8be8f6d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MarketDataRevenueMember_019dd9a5-d910-764f-aa28-0f0c0196fcaa" xlink:href="tw-20260630.xsd#tw_MarketDataRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-701f-a23f-63ec69ed238e" xlink:to="loc_tw_MarketDataRevenueMember_019dd9a5-d910-764f-aa28-0f0c0196fcaa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d910-75c9-a1fd-c0f1a3c1fa77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-701f-a23f-63ec69ed238e" xlink:to="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d910-75c9-a1fd-c0f1a3c1fa77" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019dd9a5-d910-7b64-a4c8-8f855f1bcb05" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_RevenuesAbstract_019dd9a5-d910-7b64-a4c8-8f855f1bcb05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d910-7485-942e-ee3989d43a3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019dd9a5-d910-7b64-a4c8-8f855f1bcb05" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d910-7485-942e-ee3989d43a3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019dd9a5-d910-7705-bd35-6804e3006b8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019dd9a5-d910-7705-bd35-6804e3006b8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019dd9a5-d910-7cff-850f-bec17c0c92f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_DepreciationAndAmortization_019dd9a5-d910-7cff-850f-bec17c0c92f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_019dd9a5-d910-71ca-9084-d41c1f53957c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommunicationsAndInformationTechnology"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_019dd9a5-d910-71ca-9084-d41c1f53957c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019dd9a5-d910-7093-830b-d276d1b3ca42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019dd9a5-d910-7093-830b-d276d1b3ca42" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019dd9a5-d910-7813-8ee1-875a3102d566" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_ProfessionalFees_019dd9a5-d910-7813-8ee1-875a3102d566" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_019dd9a5-d910-7775-9a3c-cd9f50d15413" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OccupancyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_OccupancyNet_019dd9a5-d910-7775-9a3c-cd9f50d15413" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019dd9a5-d910-78ae-84a6-d109dcb993b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019dd9a5-d910-75e6-b4f9-104b6effb719" xlink:to="loc_us-gaap_CostsAndExpenses_019dd9a5-d910-78ae-84a6-d109dcb993b1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019dd9a5-d910-7f40-a24a-f46209ce4b96" 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_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_OperatingIncomeLoss_019dd9a5-d910-7f40-a24a-f46209ce4b96" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterestAndDividend_019dd9a5-d910-7be3-a5c0-039bad6955ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInterestAndDividend"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_InvestmentIncomeInterestAndDividend_019dd9a5-d910-7be3-a5c0-039bad6955ab" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019dd9a5-d910-78ed-8a90-3d65fb6dd39c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019dd9a5-d910-78ed-8a90-3d65fb6dd39c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019dd9a5-d910-7544-8e38-ce5149d7d0b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019dd9a5-d910-7544-8e38-ce5149d7d0b1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019dd9a5-d910-74d9-88f8-32c21dace724" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019dd9a5-d910-74d9-88f8-32c21dace724" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019dd9a5-d910-7fd2-9e74-c00aea969345" 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_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019dd9a5-d910-7fd2-9e74-c00aea969345" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019dd9a5-d910-7900-8398-84293dc8c74b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_ProfitLoss_019dd9a5-d910-7900-8398-84293dc8c74b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019dd9a5-d910-7ebe-9b3e-3f6cff56a847" 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_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019dd9a5-d910-7ebe-9b3e-3f6cff56a847" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019dd9a5-d910-7981-9fbc-c90e643fe8f0" 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_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_NetIncomeLoss_019dd9a5-d910-7981-9fbc-c90e643fe8f0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_019dd9a5-d910-78b8-a8e0-1d721e1081a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_EarningsPerShareAbstract_019dd9a5-d910-78b8-a8e0-1d721e1081a2" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019dd9a5-d910-7b14-8823-a77acc77edc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019dd9a5-d910-78b8-a8e0-1d721e1081a2" xlink:to="loc_us-gaap_EarningsPerShareBasic_019dd9a5-d910-7b14-8823-a77acc77edc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019dd9a5-d910-7899-9fb6-51a4ba671247" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019dd9a5-d910-78b8-a8e0-1d721e1081a2" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019dd9a5-d910-7899-9fb6-51a4ba671247" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019dd9a5-d910-7304-b082-d1c39115abba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-71d6-9529-44b4895472e0" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019dd9a5-d910-7304-b082-d1c39115abba" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019dd9a5-d910-72b6-a5e6-b2136fb193ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019dd9a5-d910-7304-b082-d1c39115abba" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019dd9a5-d910-72b6-a5e6-b2136fb193ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019dd9a5-d910-7f3d-80d5-71f1d00e57d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_019dd9a5-d910-7304-b082-d1c39115abba" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019dd9a5-d910-7f3d-80d5-71f1d00e57d4" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofChangesinEquity" xlink:type="simple" xlink:href="tw-20260630.xsd#CondensedConsolidatedStatementsofChangesinEquity"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofChangesinEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019dd9a5-d910-70cd-a5f0-d50e8eb12c65" 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_019dd9a5-d910-75c5-979e-f22b36297d77" 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_019dd9a5-d910-70cd-a5f0-d50e8eb12c65" xlink:to="loc_us-gaap_StatementTable_019dd9a5-d910-75c5-979e-f22b36297d77" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019dd9a5-d910-7286-9d11-6a504b5ee274" 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_019dd9a5-d910-75c5-979e-f22b36297d77" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019dd9a5-d910-7286-9d11-6a504b5ee274" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7286-9d11-6a504b5ee274_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_019dd9a5-d910-7286-9d11-6a504b5ee274" xlink:to="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7286-9d11-6a504b5ee274_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" 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_019dd9a5-d910-7286-9d11-6a504b5ee274" xlink:to="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019dd9a5-d910-74d1-bf01-9bced02cfeab" 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_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" xlink:to="loc_us-gaap_CommonStockMember_019dd9a5-d910-74d1-bf01-9bced02cfeab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019dd9a5-d910-7c25-b81a-ff26fb8f8e57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019dd9a5-d910-7c25-b81a-ff26fb8f8e57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019dd9a5-d910-77c2-819e-1047db8498f2" 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_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019dd9a5-d910-77c2-819e-1047db8498f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019dd9a5-d910-794b-8d10-f1d3d71b2e09" 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_EquityComponentDomain_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" xlink:to="loc_us-gaap_RetainedEarningsMember_019dd9a5-d910-794b-8d10-f1d3d71b2e09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019dd9a5-d910-7d31-9ec5-7d3b1cc7613c" 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_019dd9a5-d910-7450-ac9e-e16f4f02b4d9" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019dd9a5-d910-7d31-9ec5-7d3b1cc7613c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-706a-9551-ebf882c71829" 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_us-gaap_StatementTable_019dd9a5-d910-75c5-979e-f22b36297d77" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-706a-9551-ebf882c71829" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-706a-9551-ebf882c71829_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_019dd9a5-d910-706a-9551-ebf882c71829" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-706a-9551-ebf882c71829_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7378-9552-77e59dd337ec" 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_019dd9a5-d910-706a-9551-ebf882c71829" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7378-9552-77e59dd337ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7eca-879d-801b3f988d4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7378-9552-77e59dd337ec" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7eca-879d-801b3f988d4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-73f4-a4a3-92bb81c0f073" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7378-9552-77e59dd337ec" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-73f4-a4a3-92bb81c0f073" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_019dd9a5-d910-74d9-aa49-921bd38a86b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7378-9552-77e59dd337ec" xlink:to="loc_us-gaap_CommonClassCMember_019dd9a5-d910-74d9-aa49-921bd38a86b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CommonClassDMember_019dd9a5-d910-7094-a17a-cbffec8dba9e" xlink:href="tw-20260630.xsd#tw_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7378-9552-77e59dd337ec" xlink:to="loc_tw_CommonClassDMember_019dd9a5-d910-7094-a17a-cbffec8dba9e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" 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_019dd9a5-d910-70cd-a5f0-d50e8eb12c65" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019dd9a5-d910-7aa1-a75d-5b10886f799a" 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_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019dd9a5-d910-7aa1-a75d-5b10886f799a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019dd9a5-d910-7f1b-98c6-3da62cbec366" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019dd9a5-d910-7f1b-98c6-3da62cbec366" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019dd9a5-d910-736b-8060-807c52c95e9a" 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_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019dd9a5-d910-736b-8060-807c52c95e9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_AdjustmentsToAdditionalPaidInCapitalTaxReceivableAgreementLiabilityAndDeferredTaxesReorganizationTransactionAndIpo_019dd9a5-d910-784e-82d2-95dc00403141" xlink:href="tw-20260630.xsd#tw_AdjustmentsToAdditionalPaidInCapitalTaxReceivableAgreementLiabilityAndDeferredTaxesReorganizationTransactionAndIpo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_tw_AdjustmentsToAdditionalPaidInCapitalTaxReceivableAgreementLiabilityAndDeferredTaxesReorganizationTransactionAndIpo_019dd9a5-d910-784e-82d2-95dc00403141" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MinorityInterestIncreaseDecreaseFromAdjustments_019dd9a5-d910-75ad-9bc8-37a1d5b1045c" xlink:href="tw-20260630.xsd#tw_MinorityInterestIncreaseDecreaseFromAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_tw_MinorityInterestIncreaseDecreaseFromAdjustments_019dd9a5-d910-75ad-9bc8-37a1d5b1045c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019dd9a5-d910-742b-8265-2bbef28de42f" 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_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019dd9a5-d910-742b-8265-2bbef28de42f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_019dd9a5-d910-7eba-af2d-60eda063795e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Dividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_Dividends_019dd9a5-d910-7eba-af2d-60eda063795e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019dd9a5-d910-76fc-bdaa-64fbb2abc86e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019dd9a5-d910-76fc-bdaa-64fbb2abc86e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019dd9a5-d910-754e-a617-aac3ba221483" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019dd9a5-d910-754e-a617-aac3ba221483" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019dd9a5-d910-7027-99b0-7d9c73bb3441" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_ProfitLoss_019dd9a5-d910-7027-99b0-7d9c73bb3441" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019dd9a5-d910-7327-9576-553b7d46a075" 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_019dd9a5-d910-7ec7-bf45-53448f70c248" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019dd9a5-d910-7327-9576-553b7d46a075" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019dd9a5-d910-7465-adbf-f330f9cfe91d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="tw-20260630.xsd#CondensedConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" 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_019dd9a5-d910-7a78-ad8d-a0444a7aaf5e" 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_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_StatementTable_019dd9a5-d910-7a78-ad8d-a0444a7aaf5e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentAxis_019dd9a5-d910-7971-85d0-736d6bbbfa94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrecurringAdjustmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019dd9a5-d910-7a78-ad8d-a0444a7aaf5e" xlink:to="loc_us-gaap_NonrecurringAdjustmentAxis_019dd9a5-d910-7971-85d0-736d6bbbfa94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_019dd9a5-d910-7971-85d0-736d6bbbfa94_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrecurringAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_019dd9a5-d910-7971-85d0-736d6bbbfa94" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_019dd9a5-d910-7971-85d0-736d6bbbfa94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_019dd9a5-d910-7bbe-ba89-e8a0c49249e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrecurringAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_019dd9a5-d910-7971-85d0-736d6bbbfa94" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_019dd9a5-d910-7bbe-ba89-e8a0c49249e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_AdjustedForRefinitivTransactionMember_019dd9a5-d910-764e-809b-942ed5d4450d" xlink:href="tw-20260630.xsd#tw_AdjustedForRefinitivTransactionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_019dd9a5-d910-7bbe-ba89-e8a0c49249e7" xlink:to="loc_tw_AdjustedForRefinitivTransactionMember_019dd9a5-d910-764e-809b-942ed5d4450d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7d27-890f-6fff4a9682c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7d27-890f-6fff4a9682c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019dd9a5-d910-74db-8e9d-0396b845b743" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7d27-890f-6fff4a9682c6" xlink:to="loc_us-gaap_ProfitLoss_019dd9a5-d910-74db-8e9d-0396b845b743" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7d27-890f-6fff4a9682c6" xlink:to="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019dd9a5-d910-7af9-9303-2f2f4630c6d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_us-gaap_DepreciationAndAmortization_019dd9a5-d910-7af9-9303-2f2f4630c6d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019dd9a5-d910-73c1-aa05-1f5214da4337" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_us-gaap_ShareBasedCompensation_019dd9a5-d910-73c1-aa05-1f5214da4337" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DigitalAssetsReceivedAsRevenue_019dd9a5-d910-7893-a863-3d804b766cfc" xlink:href="tw-20260630.xsd#tw_DigitalAssetsReceivedAsRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_tw_DigitalAssetsReceivedAsRevenue_019dd9a5-d910-7893-a863-3d804b766cfc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019dd9a5-d910-7dca-bc49-1ff23b16fd49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019dd9a5-d910-7dca-bc49-1ff23b16fd49" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_019dd9a5-d910-71d4-a6dd-f6a0fecf48b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_019dd9a5-d910-71d4-a6dd-f6a0fecf48b4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOperatingAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInBrokerageReceivables_019dd9a5-d910-7ec0-b470-5a25ad76f7b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInBrokerageReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:to="loc_us-gaap_IncreaseDecreaseInBrokerageReceivables_019dd9a5-d910-7ec0-b470-5a25ad76f7b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDepositOtherAssets_019dd9a5-d910-7c2b-ac26-5177dd77861c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInDepositOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:to="loc_us-gaap_IncreaseDecreaseInDepositOtherAssets_019dd9a5-d910-7c2b-ac26-5177dd77861c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019dd9a5-d910-7f6c-bc6e-13c01f8025e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019dd9a5-d910-7f6c-bc6e-13c01f8025e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseDueFromAffiliates_019dd9a5-d910-7dcd-80b4-1780b7d70b2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseDueFromAffiliates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:to="loc_us-gaap_IncreaseDecreaseDueFromAffiliates_019dd9a5-d910-7dcd-80b4-1780b7d70b2c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_IncreaseDecreaseInDeferredTaxAssets_019dd9a5-d910-71b2-9e66-6975c4a85234" xlink:href="tw-20260630.xsd#tw_IncreaseDecreaseInDeferredTaxAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:to="loc_tw_IncreaseDecreaseInDeferredTaxAssets_019dd9a5-d910-71b2-9e66-6975c4a85234" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019dd9a5-d910-713b-85d4-582e4b76be39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingAssetsAbstract_019dd9a5-d910-7cb6-8694-c8a9109db326" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019dd9a5-d910-713b-85d4-582e4b76be39" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract_019dd9a5-d910-7bdb-a877-4fd2adbe3f4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7b0c-8352-6d6d76015318" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract_019dd9a5-d910-7bdb-a877-4fd2adbe3f4f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_019dd9a5-d910-73f1-a60c-f7d3b49642e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract_019dd9a5-d910-7bdb-a877-4fd2adbe3f4f" xlink:to="loc_us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_019dd9a5-d910-73f1-a60c-f7d3b49642e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_019dd9a5-d910-7d41-bc71-2fe353bf6cd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract_019dd9a5-d910-7bdb-a877-4fd2adbe3f4f" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_019dd9a5-d910-7d41-bc71-2fe353bf6cd2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019dd9a5-d910-7b3e-84a0-8487ee45c591" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract_019dd9a5-d910-7bdb-a877-4fd2adbe3f4f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019dd9a5-d910-7b3e-84a0-8487ee45c591" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019dd9a5-d910-7669-811a-24dc0a01fcf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019dd9a5-d910-7d27-890f-6fff4a9682c6" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019dd9a5-d910-7669-811a-24dc0a01fcf1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019dd9a5-d910-75fe-b16d-e6ccad096938" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019dd9a5-d910-75fe-b16d-e6ccad096938" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireInvestments_019dd9a5-d910-7847-9380-827ebd27c5d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019dd9a5-d910-75fe-b16d-e6ccad096938" xlink:to="loc_us-gaap_PaymentsToAcquireInvestments_019dd9a5-d910-7847-9380-827ebd27c5d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019dd9a5-d910-7b2a-8d87-acf530d9100c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019dd9a5-d910-75fe-b16d-e6ccad096938" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019dd9a5-d910-7b2a-8d87-acf530d9100c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForSoftware_019dd9a5-d910-7eb3-a8bf-b52f8c792e5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForSoftware"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019dd9a5-d910-75fe-b16d-e6ccad096938" xlink:to="loc_us-gaap_PaymentsForSoftware_019dd9a5-d910-7eb3-a8bf-b52f8c792e5e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019dd9a5-d910-75c7-a718-1549ef53b764" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019dd9a5-d910-75fe-b16d-e6ccad096938" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019dd9a5-d910-75c7-a718-1549ef53b764" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019dd9a5-d910-7fbf-9e64-b42f6aa2c16a" 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_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019dd9a5-d910-7fbf-9e64-b42f6aa2c16a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_019dd9a5-d910-7531-a271-8f04ffc9d9de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_019dd9a5-d910-7531-a271-8f04ffc9d9de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfOrdinaryDividends_019dd9a5-d910-77e6-b482-cd32bce4c791" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfOrdinaryDividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_us-gaap_PaymentsOfOrdinaryDividends_019dd9a5-d910-77e6-b482-cd32bce4c791" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_PaymentsOfCapitalDistributionToNoncontrollingInterest_019dd9a5-d910-707c-9d6f-744d59e2e86a" xlink:href="tw-20260630.xsd#tw_PaymentsOfCapitalDistributionToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_tw_PaymentsOfCapitalDistributionToNoncontrollingInterest_019dd9a5-d910-707c-9d6f-744d59e2e86a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019dd9a5-d910-79f9-a8a3-ad7e6832c3cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019dd9a5-d910-79f9-a8a3-ad7e6832c3cb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_PaymentsOnTaxReceivableAgreementLiability_019dd9a5-d910-7c1b-9efb-7e425f1f8875" xlink:href="tw-20260630.xsd#tw_PaymentsOnTaxReceivableAgreementLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_tw_PaymentsOnTaxReceivableAgreementLiability_019dd9a5-d910-7c1b-9efb-7e425f1f8875" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019dd9a5-d910-70ea-b940-b811014a1e12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019dd9a5-d910-7b8d-b1e0-ecaa0dcca815" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019dd9a5-d910-70ea-b940-b811014a1e12" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_019dd9a5-d910-75eb-bef8-548b6f2e25cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_019dd9a5-d910-75eb-bef8-548b6f2e25cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019dd9a5-d910-7400-b941-69317b5965b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019dd9a5-d910-7400-b941-69317b5965b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract_019dd9a5-d910-7cc2-8563-9b13a3adf1f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract_019dd9a5-d910-7cc2-8563-9b13a3adf1f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019dd9a5-d910-7e01-943c-29366cb4cfa6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract_019dd9a5-d910-7cc2-8563-9b13a3adf1f2" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019dd9a5-d910-7e01-943c-29366cb4cfa6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019dd9a5-d910-7859-bc82-6f7bd9d37620" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_019dd9a5-d910-7a9b-b21d-93784af7572f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_019dd9a5-d910-7a9b-b21d-93784af7572f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_019dd9a5-d910-7528-9111-f2a29fc53bfa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_019dd9a5-d910-7a9b-b21d-93784af7572f" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_019dd9a5-d910-7528-9111-f2a29fc53bfa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_019dd9a5-d910-769a-b810-fd4436dd3dee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_019dd9a5-d910-7a9b-b21d-93784af7572f" xlink:to="loc_us-gaap_InterestPaidNet_019dd9a5-d910-769a-b810-fd4436dd3dee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySecuritiesReceivedUponConversionOfReceivables_019dd9a5-d910-7133-b6af-16e681964f60" xlink:href="tw-20260630.xsd#tw_EquitySecuritiesReceivedUponConversionOfReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:to="loc_tw_EquitySecuritiesReceivedUponConversionOfReceivables_019dd9a5-d910-7133-b6af-16e681964f60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_019dd9a5-d910-7a4d-a314-0490cfe1782b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_019dd9a5-d910-7a4d-a314-0490cfe1782b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_UnsettledShareRepurchasesAndExciseTaxIncludedInOtherLiabilities_019dd9a5-d910-7c05-8323-31245ed92c90" xlink:href="tw-20260630.xsd#tw_UnsettledShareRepurchasesAndExciseTaxIncludedInOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:to="loc_tw_UnsettledShareRepurchasesAndExciseTaxIncludedInOtherLiabilities_019dd9a5-d910-7c05-8323-31245ed92c90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAssumed1_019dd9a5-d910-7c55-a727-05ebcec42f2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAssumed1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:to="loc_us-gaap_LiabilitiesAssumed1_019dd9a5-d910-7c55-a727-05ebcec42f2b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeTaxExpense_019dd9a5-d910-7b85-8178-616d4d218708" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNoncashIncomeTaxExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_019dd9a5-d910-7eae-8f5a-79fb002fe872" xlink:to="loc_us-gaap_OtherNoncashIncomeTaxExpense_019dd9a5-d910-7b85-8178-616d4d218708" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalCashFlowElementsAndSupplementalCashFlowInformationAbstract_019dd9a5-d910-7c1f-ba2d-cb1b6cbb2c18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalCashFlowElementsAndSupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019dd9a5-d910-7738-884e-b82e2ba6e775" xlink:to="loc_us-gaap_AdditionalCashFlowElementsAndSupplementalCashFlowInformationAbstract_019dd9a5-d910-7c1f-ba2d-cb1b6cbb2c18" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019dd9a5-d910-7427-bb34-4f5df456c1cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdditionalCashFlowElementsAndSupplementalCashFlowInformationAbstract_019dd9a5-d910-7c1f-ba2d-cb1b6cbb2c18" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019dd9a5-d910-7427-bb34-4f5df456c1cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_019dd9a5-d910-7c54-bc0c-9748e2022c06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdditionalCashFlowElementsAndSupplementalCashFlowInformationAbstract_019dd9a5-d910-7c1f-ba2d-cb1b6cbb2c18" xlink:to="loc_us-gaap_RestrictedCash_019dd9a5-d910-7c54-bc0c-9748e2022c06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019dd9a5-d910-7658-a0ef-12e3dec480eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/OrganizationDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#OrganizationDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/OrganizationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019dd9a5-d910-72d6-b15b-3e1d796e0e92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019dd9a5-d910-72d6-b15b-3e1d796e0e92" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019dd9a5-d910-74bd-9e10-dae1acc96b41" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019dd9a5-d910-72d6-b15b-3e1d796e0e92" xlink:to="loc_srt_OwnershipAxis_019dd9a5-d910-74bd-9e10-dae1acc96b41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019dd9a5-d910-74bd-9e10-dae1acc96b41_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019dd9a5-d910-74bd-9e10-dae1acc96b41" xlink:to="loc_srt_OwnershipDomain_019dd9a5-d910-74bd-9e10-dae1acc96b41_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019dd9a5-d910-7b0f-a528-dc74c9492dab" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019dd9a5-d910-74bd-9e10-dae1acc96b41" xlink:to="loc_srt_OwnershipDomain_019dd9a5-d910-7b0f-a528-dc74c9492dab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebMarketsLLCMember_019dd9a5-d910-72d3-bc5c-15ae6d7cd64d" xlink:href="tw-20260630.xsd#tw_TradewebMarketsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019dd9a5-d910-7b0f-a528-dc74c9492dab" xlink:to="loc_tw_TradewebMarketsLLCMember_019dd9a5-d910-72d3-bc5c-15ae6d7cd64d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebMarketsIncMember_019dd9a5-d910-715a-98ac-13838c6434ff" xlink:href="tw-20260630.xsd#tw_TradewebMarketsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019dd9a5-d910-7b0f-a528-dc74c9492dab" xlink:to="loc_tw_TradewebMarketsIncMember_019dd9a5-d910-715a-98ac-13838c6434ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-70f8-924d-7dee22fb9ff9" 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_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019dd9a5-d910-72d6-b15b-3e1d796e0e92" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-70f8-924d-7dee22fb9ff9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-70f8-924d-7dee22fb9ff9_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_019dd9a5-d910-70f8-924d-7dee22fb9ff9" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-70f8-924d-7dee22fb9ff9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7b50-b153-174dbb73d0ac" 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_019dd9a5-d910-70f8-924d-7dee22fb9ff9" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7b50-b153-174dbb73d0ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7c6e-b4e6-99efc36050a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7b50-b153-174dbb73d0ac" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7c6e-b4e6-99efc36050a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-783b-90c8-a48cee4811d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7b50-b153-174dbb73d0ac" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-783b-90c8-a48cee4811d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7f64-9c5e-9c2533e58b32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7b50-b153-174dbb73d0ac" xlink:to="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7f64-9c5e-9c2533e58b32" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CommonClassDMember_019dd9a5-d910-7f4e-9cac-7c9f10d31599" xlink:href="tw-20260630.xsd#tw_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7b50-b153-174dbb73d0ac" xlink:to="loc_tw_CommonClassDMember_019dd9a5-d910-7f4e-9cac-7c9f10d31599" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_019dd9a5-d910-75c5-b2f7-15ee5989f609" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019dd9a5-d910-72d6-b15b-3e1d796e0e92" xlink:to="loc_srt_TitleOfIndividualAxis_019dd9a5-d910-75c5-b2f7-15ee5989f609" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_019dd9a5-d910-75c5-b2f7-15ee5989f609_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_019dd9a5-d910-75c5-b2f7-15ee5989f609" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_019dd9a5-d910-75c5-b2f7-15ee5989f609_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_019dd9a5-d910-779b-b18a-c2589bd0e425" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_019dd9a5-d910-75c5-b2f7-15ee5989f609" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_019dd9a5-d910-779b-b18a-c2589bd0e425" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_PublicInvestorsMember_019dd9a5-d910-74cc-95dd-f972ecc97cd7" xlink:href="tw-20260630.xsd#tw_PublicInvestorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_019dd9a5-d910-779b-b18a-c2589bd0e425" xlink:to="loc_tw_PublicInvestorsMember_019dd9a5-d910-74cc-95dd-f972ecc97cd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_OtherStockholdersMember_019dd9a5-d910-78a1-bf2f-955cb6bdf6ca" xlink:href="tw-20260630.xsd#tw_OtherStockholdersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_019dd9a5-d910-779b-b18a-c2589bd0e425" xlink:to="loc_tw_OtherStockholdersMember_019dd9a5-d910-78a1-bf2f-955cb6bdf6ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019dd9a5-d910-722c-8b5f-2179b11ccc89" 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_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019dd9a5-d910-72d6-b15b-3e1d796e0e92" xlink:to="loc_dei_LegalEntityAxis_019dd9a5-d910-722c-8b5f-2179b11ccc89" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019dd9a5-d910-722c-8b5f-2179b11ccc89_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_019dd9a5-d910-722c-8b5f-2179b11ccc89" xlink:to="loc_dei_EntityDomain_019dd9a5-d910-722c-8b5f-2179b11ccc89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019dd9a5-d910-7a8b-9241-47a76373c07d" 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_019dd9a5-d910-722c-8b5f-2179b11ccc89" xlink:to="loc_dei_EntityDomain_019dd9a5-d910-7a8b-9241-47a76373c07d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_LSEGMember_019dd9a5-d910-7c1a-82ea-cf31a7b0649b" xlink:href="tw-20260630.xsd#tw_LSEGMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019dd9a5-d910-7a8b-9241-47a76373c07d" xlink:to="loc_tw_LSEGMember_019dd9a5-d910-7c1a-82ea-cf31a7b0649b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_019dd9a5-d910-73b1-a98f-cb09179d472e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_019dd9a5-d910-73b1-a98f-cb09179d472e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_019dd9a5-d910-7c85-a72b-f18dc69f2b45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_019dd9a5-d910-7c85-a72b-f18dc69f2b45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019dd9a5-d910-78d8-969f-c5ccf5cc2320" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019dd9a5-d910-78d8-969f-c5ccf5cc2320" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_019dd9a5-d910-768a-943a-144d23763c5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityNoteStockSplitConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_019dd9a5-d910-768a-943a-144d23763c5f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_NumberOfInvestmentProviders_019dd9a5-d910-7ccb-badb-c89cfeaf2a73" xlink:href="tw-20260630.xsd#tw_NumberOfInvestmentProviders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_tw_NumberOfInvestmentProviders_019dd9a5-d910-7ccb-badb-c89cfeaf2a73" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_NumberOfShareOwned_019dd9a5-d910-7c97-b5c0-b82e75bf245c" xlink:href="tw-20260630.xsd#tw_NumberOfShareOwned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_tw_NumberOfShareOwned_019dd9a5-d910-7c97-b5c0-b82e75bf245c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_VotingPowerPercentage_019dd9a5-d910-729c-976a-3307b5a92f18" xlink:href="tw-20260630.xsd#tw_VotingPowerPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_tw_VotingPowerPercentage_019dd9a5-d910-729c-976a-3307b5a92f18" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossShares_019dd9a5-d910-7bd5-9600-c86776ada33c" xlink:href="tw-20260630.xsd#tw_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_tw_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossShares_019dd9a5-d910-7bd5-9600-c86776ada33c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019dd9a5-d910-7d65-843b-0e37274d0c21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019dd9a5-d910-7b48-936d-44b6364c8c26" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019dd9a5-d910-7d65-843b-0e37274d0c21" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/SignificantAccountingPoliciesFurnitureEquipmentPurchasedSoftwareLeaseholdImprovementsandSoftwareDevelopmentCostsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#SignificantAccountingPoliciesFurnitureEquipmentPurchasedSoftwareLeaseholdImprovementsandSoftwareDevelopmentCostsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/SignificantAccountingPoliciesFurnitureEquipmentPurchasedSoftwareLeaseholdImprovementsandSoftwareDevelopmentCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019dd9a5-d910-7e0a-b514-e278c4ff0f09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019dd9a5-d910-7e0a-b514-e278c4ff0f09" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019dd9a5-d910-7cbb-bb54-bb96d771936e" 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_ScheduleOfPropertyPlantAndEquipmentTable_019dd9a5-d910-7e0a-b514-e278c4ff0f09" xlink:to="loc_srt_RangeAxis_019dd9a5-d910-7cbb-bb54-bb96d771936e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dd9a5-d910-7cbb-bb54-bb96d771936e_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_019dd9a5-d910-7cbb-bb54-bb96d771936e" xlink:to="loc_srt_RangeMember_019dd9a5-d910-7cbb-bb54-bb96d771936e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dd9a5-d910-76e8-ab03-924780b34ccc" 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_019dd9a5-d910-7cbb-bb54-bb96d771936e" xlink:to="loc_srt_RangeMember_019dd9a5-d910-76e8-ab03-924780b34ccc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019dd9a5-d910-7b95-bf5e-060d053279a4" 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_019dd9a5-d910-76e8-ab03-924780b34ccc" xlink:to="loc_srt_MinimumMember_019dd9a5-d910-7b95-bf5e-060d053279a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019dd9a5-d910-78e1-bf72-9047a5c98bf5" 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_019dd9a5-d910-76e8-ab03-924780b34ccc" xlink:to="loc_srt_MaximumMember_019dd9a5-d910-78e1-bf72-9047a5c98bf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dd9a5-d910-7cd0-9a49-7fc01ac2500b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019dd9a5-d910-7e0a-b514-e278c4ff0f09" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dd9a5-d910-7cd0-9a49-7fc01ac2500b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dd9a5-d910-7cd0-9a49-7fc01ac2500b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dd9a5-d910-7cd0-9a49-7fc01ac2500b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dd9a5-d910-7cd0-9a49-7fc01ac2500b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dd9a5-d910-7b22-bcb3-6aaaf3cb5936" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dd9a5-d910-7cd0-9a49-7fc01ac2500b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dd9a5-d910-7b22-bcb3-6aaaf3cb5936" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_019e221f-944e-7587-be3a-63b0408743a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dd9a5-d910-7b22-bcb3-6aaaf3cb5936" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_019e221f-944e-7587-be3a-63b0408743a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_IntangibleAssetsExcludingInternallyDevelopedSoftwareMember_019f1480-30c9-708f-8d52-0483a38bd88e" xlink:href="tw-20260630.xsd#tw_IntangibleAssetsExcludingInternallyDevelopedSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dd9a5-d910-7b22-bcb3-6aaaf3cb5936" xlink:to="loc_tw_IntangibleAssetsExcludingInternallyDevelopedSoftwareMember_019f1480-30c9-708f-8d52-0483a38bd88e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019dd9a5-d910-7e85-bccd-aae06f33fcd1" 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_ScheduleOfPropertyPlantAndEquipmentTable_019dd9a5-d910-7e0a-b514-e278c4ff0f09" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019dd9a5-d910-7e85-bccd-aae06f33fcd1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-7e85-bccd-aae06f33fcd1_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_019dd9a5-d910-7e85-bccd-aae06f33fcd1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-7e85-bccd-aae06f33fcd1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-781a-b577-c66fc15ca540" 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_019dd9a5-d910-7e85-bccd-aae06f33fcd1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-781a-b577-c66fc15ca540" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ICDMember_019dd9a5-d910-7a3b-9746-2da4508cb179" xlink:href="tw-20260630.xsd#tw_ICDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-781a-b577-c66fc15ca540" xlink:to="loc_tw_ICDMember_019dd9a5-d910-7a3b-9746-2da4508cb179" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_R8FinMember_019dd9a5-d910-76be-b9b8-1cb653aa4f35" xlink:href="tw-20260630.xsd#tw_R8FinMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-781a-b577-c66fc15ca540" xlink:to="loc_tw_R8FinMember_019dd9a5-d910-76be-b9b8-1cb653aa4f35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_YieldbrokerAcquisitionMember_019dd9a5-d910-74ed-8510-9852ea6951d3" xlink:href="tw-20260630.xsd#tw_YieldbrokerAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-781a-b577-c66fc15ca540" xlink:to="loc_tw_YieldbrokerAcquisitionMember_019dd9a5-d910-74ed-8510-9852ea6951d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_NFIAcquisitionMember_019dd9a5-d910-78a2-872b-d7267999909c" xlink:href="tw-20260630.xsd#tw_NFIAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dd9a5-d910-781a-b577-c66fc15ca540" xlink:to="loc_tw_NFIAcquisitionMember_019dd9a5-d910-78a2-872b-d7267999909c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_019dd9a5-d910-7700-b2aa-36ce284c0e6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_019dd9a5-d910-7700-b2aa-36ce284c0e6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019dd9a5-d910-706a-b9d5-2b8e3b6632e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019dd9a5-d910-706a-b9d5-2b8e3b6632e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_019dd9a5-d910-7238-ab7f-c08841400546" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_Depreciation_019dd9a5-d910-7238-ab7f-c08841400546" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019dd9a5-d910-7743-a3e7-af887a2b9e47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019dd9a5-d910-7743-a3e7-af887a2b9e47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_AmortizationPeriodPushdownAccountingAdjustment_019dd9a5-d910-7c86-96e6-b0e2e8740e1a" xlink:href="tw-20260630.xsd#tw_AmortizationPeriodPushdownAccountingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_tw_AmortizationPeriodPushdownAccountingAdjustment_019dd9a5-d910-7c86-96e6-b0e2e8740e1a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019f147d-e1ba-7ff1-a68f-e897922ea387" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019f147d-e1ba-7ff1-a68f-e897922ea387" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019f147d-e1ba-7f93-9a87-aee1d584fb6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019dd9a5-d910-7e94-9957-606d73b11518" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019f147d-e1ba-7f93-9a87-aee1d584fb6b" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/SignificantAccountingPoliciesIntangibleAssetsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#SignificantAccountingPoliciesIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/SignificantAccountingPoliciesIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dd9a5-d910-777b-8ec0-c98e5808ea4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019dd9a5-d910-716e-a820-f905b6b081e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dd9a5-d910-777b-8ec0-c98e5808ea4f" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019dd9a5-d910-716e-a820-f905b6b081e9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019dd9a5-d910-7999-9055-08e36c03c153" 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_ScheduleOfFiniteLivedIntangibleAssetsTable_019dd9a5-d910-716e-a820-f905b6b081e9" xlink:to="loc_srt_RangeAxis_019dd9a5-d910-7999-9055-08e36c03c153" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dd9a5-d910-7999-9055-08e36c03c153_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_019dd9a5-d910-7999-9055-08e36c03c153" xlink:to="loc_srt_RangeMember_019dd9a5-d910-7999-9055-08e36c03c153_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dd9a5-d910-7f63-9237-d0fa98775036" 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_019dd9a5-d910-7999-9055-08e36c03c153" xlink:to="loc_srt_RangeMember_019dd9a5-d910-7f63-9237-d0fa98775036" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019dd9a5-d910-721a-b2b3-b77a1c949373" 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_019dd9a5-d910-7f63-9237-d0fa98775036" xlink:to="loc_srt_MinimumMember_019dd9a5-d910-721a-b2b3-b77a1c949373" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019dd9a5-d910-7682-8b2d-1dbe18c9baaa" 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_019dd9a5-d910-7f63-9237-d0fa98775036" xlink:to="loc_srt_MaximumMember_019dd9a5-d910-7682-8b2d-1dbe18c9baaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019dd9a5-d910-779b-8e28-79aed0c6c1b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dd9a5-d910-777b-8ec0-c98e5808ea4f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019dd9a5-d910-779b-8e28-79aed0c6c1b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019dd9a5-d910-7227-b3d3-b34cce6abb67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dd9a5-d910-777b-8ec0-c98e5808ea4f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019dd9a5-d910-7227-b3d3-b34cce6abb67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019dd9a5-d910-7340-a43b-a806fc7fe91b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dd9a5-d910-777b-8ec0-c98e5808ea4f" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019dd9a5-d910-7340-a43b-a806fc7fe91b" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/SignificantAccountingPoliciesTranslationofForeignCurrencyandExchangeDerivativeContractsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#SignificantAccountingPoliciesTranslationofForeignCurrencyandExchangeDerivativeContractsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/SignificantAccountingPoliciesTranslationofForeignCurrencyandExchangeDerivativeContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:to="loc_us-gaap_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d910-7ae6-8034-c275228cf7cd" 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_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d910-7ae6-8034-c275228cf7cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-7ae6-8034-c275228cf7cd_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_019dd9a5-d910-7ae6-8034-c275228cf7cd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-7ae6-8034-c275228cf7cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-71bb-a7e6-77b87ad65834" 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_019dd9a5-d910-7ae6-8034-c275228cf7cd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-71bb-a7e6-77b87ad65834" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d910-74b2-9f99-30a36a86836d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-71bb-a7e6-77b87ad65834" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d910-74b2-9f99-30a36a86836d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019dd9a5-d910-7424-afc7-b582c7e8a61c" 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_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019dd9a5-d910-7424-afc7-b582c7e8a61c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019dd9a5-d910-7d2c-85ac-7c4a4d5caea6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019dd9a5-d910-7d2c-85ac-7c4a4d5caea6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d910-7622-90e9-fa9921a1dbe7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d910-7622-90e9-fa9921a1dbe7" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/SignificantAccountingPoliciesTranslationofForeignCurrencyandExchangeDerivativeContractsDetails_1" xlink:type="simple" xlink:href="tw-20260630.xsd#SignificantAccountingPoliciesTranslationofForeignCurrencyandExchangeDerivativeContractsDetails_1"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/SignificantAccountingPoliciesTranslationofForeignCurrencyandExchangeDerivativeContractsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:to="loc_us-gaap_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d910-7ae6-8034-c275228cf7cd" 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_DerivativeTable_019dd9a5-d910-78b3-9e32-2ede577f9e39" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d910-7ae6-8034-c275228cf7cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-7ae6-8034-c275228cf7cd_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_019dd9a5-d910-7ae6-8034-c275228cf7cd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-7ae6-8034-c275228cf7cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-71bb-a7e6-77b87ad65834" 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_019dd9a5-d910-7ae6-8034-c275228cf7cd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-71bb-a7e6-77b87ad65834" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d910-74b2-9f99-30a36a86836d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d910-71bb-a7e6-77b87ad65834" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d910-74b2-9f99-30a36a86836d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019dd9a5-d910-7d2c-85ac-7c4a4d5caea6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019dd9a5-d910-7d2c-85ac-7c4a4d5caea6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d910-7622-90e9-fa9921a1dbe7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d910-7e26-b33a-240ec6295049" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d910-7622-90e9-fa9921a1dbe7" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/RevenueScheduleofBreakdownofRevenuesBetweenFixedandVariableRevenuesDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#RevenueScheduleofBreakdownofRevenuesBetweenFixedandVariableRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/RevenueScheduleofBreakdownofRevenuesBetweenFixedandVariableRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019dd9a5-d910-7927-b2e3-17a6c307ebaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019dd9a5-d910-77a0-a9cd-3a7ee3831f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019dd9a5-d910-7927-b2e3-17a6c307ebaf" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019dd9a5-d910-77a0-a9cd-3a7ee3831f2a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019dd9a5-d910-7c01-b9ad-fd5753d10369" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerBasisOfPricingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019dd9a5-d910-77a0-a9cd-3a7ee3831f2a" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019dd9a5-d910-7c01-b9ad-fd5753d10369" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019dd9a5-d910-7c01-b9ad-fd5753d10369_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019dd9a5-d910-7c01-b9ad-fd5753d10369" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019dd9a5-d910-7c01-b9ad-fd5753d10369_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019dd9a5-d910-7157-b13d-d4e028efc292" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019dd9a5-d910-7c01-b9ad-fd5753d10369" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019dd9a5-d910-7157-b13d-d4e028efc292" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_VariablePricingMember_019dd9a5-d910-7d72-9a74-ba582907e7eb" xlink:href="tw-20260630.xsd#tw_VariablePricingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019dd9a5-d910-7157-b13d-d4e028efc292" xlink:to="loc_tw_VariablePricingMember_019dd9a5-d910-7d72-9a74-ba582907e7eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedPriceContractMember_019dd9a5-d910-7265-adc8-aa72d3fd35c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedPriceContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019dd9a5-d910-7157-b13d-d4e028efc292" xlink:to="loc_us-gaap_FixedPriceContractMember_019dd9a5-d910-7265-adc8-aa72d3fd35c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019dd9a5-d910-793b-b38f-b37d0837c8cf" 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_DisaggregationOfRevenueTable_019dd9a5-d910-77a0-a9cd-3a7ee3831f2a" xlink:to="loc_srt_ProductOrServiceAxis_019dd9a5-d910-793b-b38f-b37d0837c8cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-793b-b38f-b37d0837c8cf_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_019dd9a5-d910-793b-b38f-b37d0837c8cf" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-793b-b38f-b37d0837c8cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7ae5-9d01-91d5e6c28951" 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_019dd9a5-d910-793b-b38f-b37d0837c8cf" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7ae5-9d01-91d5e6c28951" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TransactionFeeRevenueMember_019dd9a5-d910-72f7-b29f-034d8fc030b3" xlink:href="tw-20260630.xsd#tw_TransactionFeeRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7ae5-9d01-91d5e6c28951" xlink:to="loc_tw_TransactionFeeRevenueMember_019dd9a5-d910-72f7-b29f-034d8fc030b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_SubscriptionFeeAndMarketDataRevenueMember_019dd9a5-d910-710c-b359-a9c4d223493e" xlink:href="tw-20260630.xsd#tw_SubscriptionFeeAndMarketDataRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7ae5-9d01-91d5e6c28951" xlink:to="loc_tw_SubscriptionFeeAndMarketDataRevenueMember_019dd9a5-d910-710c-b359-a9c4d223493e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MarketDataRevenueMember_019dd9a5-d910-7c84-b7a5-1d9f0c0709e6" xlink:href="tw-20260630.xsd#tw_MarketDataRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7ae5-9d01-91d5e6c28951" xlink:to="loc_tw_MarketDataRevenueMember_019dd9a5-d910-7c84-b7a5-1d9f0c0709e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d910-79ab-a64b-a6a36472884c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7ae5-9d01-91d5e6c28951" xlink:to="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d910-79ab-a64b-a6a36472884c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetAxis_019dd9a5-d910-77d8-be13-3e9a65fdacf3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019dd9a5-d910-77a0-a9cd-3a7ee3831f2a" xlink:to="loc_srt_CryptoAssetAxis_019dd9a5-d910-77d8-be13-3e9a65fdacf3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d910-77d8-be13-3e9a65fdacf3_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d910-77d8-be13-3e9a65fdacf3" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d910-77d8-be13-3e9a65fdacf3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d910-7842-8634-f3fe67062ac7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d910-77d8-be13-3e9a65fdacf3" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d910-7842-8634-f3fe67062ac7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CantonCoinsMember_019dd9a5-d910-70b6-86fa-728631e92084" xlink:href="tw-20260630.xsd#tw_CantonCoinsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d910-7842-8634-f3fe67062ac7" xlink:to="loc_tw_CantonCoinsMember_019dd9a5-d910-70b6-86fa-728631e92084" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueAbstract_019dd9a5-d910-7a7a-a085-02fe6a5db6f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019dd9a5-d910-7927-b2e3-17a6c307ebaf" xlink:to="loc_us-gaap_DisaggregationOfRevenueAbstract_019dd9a5-d910-7a7a-a085-02fe6a5db6f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d910-76d3-8156-fc1a7a760f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueAbstract_019dd9a5-d910-7a7a-a085-02fe6a5db6f0" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d910-76d3-8156-fc1a7a760f0d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/NonControllingInterestsScheduleoftheOwnershipInterestinNoncontrollingInterestDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#NonControllingInterestsScheduleoftheOwnershipInterestinNoncontrollingInterestDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/NonControllingInterestsScheduleoftheOwnershipInterestinNoncontrollingInterestDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_019dd9a5-d910-7d04-9ef8-f4334063e26d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_us-gaap_MinorityInterestTable_019dd9a5-d910-7d04-9ef8-f4334063e26d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019dd9a5-d910-74f8-9039-7af4712e5032" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_019dd9a5-d910-7d04-9ef8-f4334063e26d" xlink:to="loc_srt_OwnershipAxis_019dd9a5-d910-74f8-9039-7af4712e5032" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019dd9a5-d910-74f8-9039-7af4712e5032_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019dd9a5-d910-74f8-9039-7af4712e5032" xlink:to="loc_srt_OwnershipDomain_019dd9a5-d910-74f8-9039-7af4712e5032_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019dd9a5-d910-7aa0-afbd-69134a6eac6d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019dd9a5-d910-74f8-9039-7af4712e5032" xlink:to="loc_srt_OwnershipDomain_019dd9a5-d910-7aa0-afbd-69134a6eac6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebMarketsLLCMember_019dd9a5-d910-76e8-b4f0-6383921eec7e" xlink:href="tw-20260630.xsd#tw_TradewebMarketsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019dd9a5-d910-7aa0-afbd-69134a6eac6d" xlink:to="loc_tw_TradewebMarketsLLCMember_019dd9a5-d910-76e8-b4f0-6383921eec7e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MinorityInterestNumberOfInterestsHeldByParent_019dd9a5-d910-7d72-bf4d-113096ce7f21" xlink:href="tw-20260630.xsd#tw_MinorityInterestNumberOfInterestsHeldByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_tw_MinorityInterestNumberOfInterestsHeldByParent_019dd9a5-d910-7d72-bf4d-113096ce7f21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MinorityInterestNumberOfInterestsHeldByNoncontrollingOwners_019dd9a5-d910-737f-baaa-1aa749572535" xlink:href="tw-20260630.xsd#tw_MinorityInterestNumberOfInterestsHeldByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_tw_MinorityInterestNumberOfInterestsHeldByNoncontrollingOwners_019dd9a5-d910-737f-baaa-1aa749572535" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MinorityInterestTotalNumberOfInterests_019dd9a5-d910-7aba-967b-9553cffce6ae" xlink:href="tw-20260630.xsd#tw_MinorityInterestTotalNumberOfInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_tw_MinorityInterestTotalNumberOfInterests_019dd9a5-d910-7aba-967b-9553cffce6ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_019dd9a5-d910-7853-b9ae-963fb7178a3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_019dd9a5-d910-7853-b9ae-963fb7178a3b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_019dd9a5-d910-795f-aa4b-7c4f2d2535c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_019dd9a5-d910-795f-aa4b-7c4f2d2535c4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MinorityInterestTotalOwnershipPercentage_019dd9a5-d910-7669-8881-475c63ca6453" xlink:href="tw-20260630.xsd#tw_MinorityInterestTotalOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7f1a-910a-907e493c1218" xlink:to="loc_tw_MinorityInterestTotalOwnershipPercentage_019dd9a5-d910-7669-8881-475c63ca6453" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/NonControllingInterestsNarrativeDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#NonControllingInterestsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/NonControllingInterestsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7718-b6ec-cb78ba9fd466" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_019dd9a5-d910-7f8b-9cc7-b2788c5c7462" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7718-b6ec-cb78ba9fd466" xlink:to="loc_us-gaap_MinorityInterestTable_019dd9a5-d910-7f8b-9cc7-b2788c5c7462" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7c1a-94c1-fdfdcc288a82" 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_us-gaap_MinorityInterestTable_019dd9a5-d910-7f8b-9cc7-b2788c5c7462" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7c1a-94c1-fdfdcc288a82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7c1a-94c1-fdfdcc288a82_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_019dd9a5-d910-7c1a-94c1-fdfdcc288a82" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7c1a-94c1-fdfdcc288a82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-76cd-85a8-fb08e0041082" 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_019dd9a5-d910-7c1a-94c1-fdfdcc288a82" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-76cd-85a8-fb08e0041082" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7f68-9fea-778e7b1a0fb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-76cd-85a8-fb08e0041082" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7f68-9fea-778e7b1a0fb9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-78eb-b6f7-e0e9fc32d9f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-76cd-85a8-fb08e0041082" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-78eb-b6f7-e0e9fc32d9f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_NoncontrollingInterestConversionRatio_019dd9a5-d910-7f32-84ec-493d2989be3d" xlink:href="tw-20260630.xsd#tw_NoncontrollingInterestConversionRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019dd9a5-d910-7718-b6ec-cb78ba9fd466" xlink:to="loc_tw_NoncontrollingInterestConversionRatio_019dd9a5-d910-7f32-84ec-493d2989be3d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/StockholdersEquityandStockBasedCompensationPlansScheduleofOutstandingSharesofCommonStockDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#StockholdersEquityandStockBasedCompensationPlansScheduleofOutstandingSharesofCommonStockDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/StockholdersEquityandStockBasedCompensationPlansScheduleofOutstandingSharesofCommonStockDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-74ee-b706-90f201a91ffc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-74d0-8087-3b5372521153" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-74ee-b706-90f201a91ffc" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-74d0-8087-3b5372521153" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7051-93da-f0b3f92bb8f6" 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_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-74d0-8087-3b5372521153" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7051-93da-f0b3f92bb8f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7051-93da-f0b3f92bb8f6_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_019dd9a5-d910-7051-93da-f0b3f92bb8f6" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7051-93da-f0b3f92bb8f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-708c-8109-6ea272b07f2f" 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_019dd9a5-d910-7051-93da-f0b3f92bb8f6" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-708c-8109-6ea272b07f2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-77c1-a30d-84da8b2ee92b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-708c-8109-6ea272b07f2f" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-77c1-a30d-84da8b2ee92b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7f4d-ac1d-fb8bcad1cb73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-708c-8109-6ea272b07f2f" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d910-7f4d-ac1d-fb8bcad1cb73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7693-be4b-5f1ac898ec44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-708c-8109-6ea272b07f2f" xlink:to="loc_us-gaap_CommonClassCMember_019dd9a5-d910-7693-be4b-5f1ac898ec44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CommonClassDMember_019dd9a5-d910-709c-bace-d6c29674e271" xlink:href="tw-20260630.xsd#tw_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-708c-8109-6ea272b07f2f" xlink:to="loc_tw_CommonClassDMember_019dd9a5-d910-709c-bace-d6c29674e271" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019dd9a5-d910-7062-a1ec-c2e4843c8d33" 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_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-74d0-8087-3b5372521153" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019dd9a5-d910-7062-a1ec-c2e4843c8d33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7062-a1ec-c2e4843c8d33_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_019dd9a5-d910-7062-a1ec-c2e4843c8d33" xlink:to="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7062-a1ec-c2e4843c8d33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7f5f-a609-9f7180583ca9" 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_019dd9a5-d910-7062-a1ec-c2e4843c8d33" xlink:to="loc_us-gaap_EquityComponentDomain_019dd9a5-d910-7f5f-a609-9f7180583ca9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019dd9a5-d910-750c-8028-4302489e3d51" 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_019dd9a5-d910-7f5f-a609-9f7180583ca9" xlink:to="loc_us-gaap_CommonStockMember_019dd9a5-d910-750c-8028-4302489e3d51" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7628-9809-d7ceefea6674" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-74ee-b706-90f201a91ffc" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7628-9809-d7ceefea6674" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019dd9a5-d910-7c9d-ada6-0ebe37fe4c18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7628-9809-d7ceefea6674" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019dd9a5-d910-7c9d-ada6-0ebe37fe4c18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_019dd9a5-d910-7ab2-b817-d218103d9d94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7628-9809-d7ceefea6674" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_019dd9a5-d910-7ab2-b817-d218103d9d94" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019dd9a5-d910-7437-a85c-652abdbd0c9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019dd9a5-d910-7628-9809-d7ceefea6674" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019dd9a5-d910-7437-a85c-652abdbd0c9d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019f1394-cbea-74a0-a0dc-d71b6a198243" 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_019dd9a5-d910-7628-9809-d7ceefea6674" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019f1394-cbea-74a0-a0dc-d71b6a198243" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019dd9a5-d910-7e24-a211-729735304873" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/StockholdersEquityandStockBasedCompensationPlansNarrativeDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#StockholdersEquityandStockBasedCompensationPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/StockholdersEquityandStockBasedCompensationPlansNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7729-9b41-b3ee66362ece" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7729-9b41-b3ee66362ece" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-7401-943f-e131bcc61a67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7729-9b41-b3ee66362ece" xlink:to="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-7401-943f-e131bcc61a67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7401-943f-e131bcc61a67_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-7401-943f-e131bcc61a67" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7401-943f-e131bcc61a67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-7401-943f-e131bcc61a67" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_Omnibus2019EquityIncentivePlanMember_019dd9a5-d910-75b7-b876-f4c7cebdfaef" xlink:href="tw-20260630.xsd#tw_Omnibus2019EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:to="loc_tw_Omnibus2019EquityIncentivePlanMember_019dd9a5-d910-75b7-b876-f4c7cebdfaef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019dd9a5-d910-7c8f-8ced-b4ef34c6a199" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019dd9a5-d910-7c8f-8ced-b4ef34c6a199" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember_019dd9a5-d910-745f-88e9-4f39ee7af43b" xlink:href="tw-20260630.xsd#tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:to="loc_tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember_019dd9a5-d910-745f-88e9-4f39ee7af43b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d910-7143-8101-1cffbd7a4a35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d910-7143-8101-1cffbd7a4a35" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019dd9a5-d910-789a-9625-398bf22b9bb4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-7d3f-a6ca-633ac80f0b6b" xlink:to="loc_us-gaap_RestrictedStockMember_019dd9a5-d910-789a-9625-398bf22b9bb4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_019dd9a5-d910-7981-b75d-7fbd1c5320ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7729-9b41-b3ee66362ece" xlink:to="loc_us-gaap_GranteeStatusAxis_019dd9a5-d910-7981-b75d-7fbd1c5320ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_019dd9a5-d910-7981-b75d-7fbd1c5320ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_019dd9a5-d910-7981-b75d-7fbd1c5320ba" xlink:to="loc_us-gaap_GranteeStatusDomain_019dd9a5-d910-7981-b75d-7fbd1c5320ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_019dd9a5-d910-76b3-96f2-88e772a87808" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_019dd9a5-d910-7981-b75d-7fbd1c5320ba" xlink:to="loc_us-gaap_GranteeStatusDomain_019dd9a5-d910-76b3-96f2-88e772a87808" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_019dd9a5-d910-71cc-a346-a657b13567b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedPaymentArrangementEmployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_019dd9a5-d910-76b3-96f2-88e772a87808" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_019dd9a5-d910-71cc-a346-a657b13567b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementNonemployeeMember_019dd9a5-d910-756a-a025-f40af508b2e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedPaymentArrangementNonemployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_019dd9a5-d910-76b3-96f2-88e772a87808" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementNonemployeeMember_019dd9a5-d910-756a-a025-f40af508b2e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_019dd9a5-d910-738f-9176-512f059381ff" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7729-9b41-b3ee66362ece" xlink:to="loc_srt_ShareRepurchaseProgramAxis_019dd9a5-d910-738f-9176-512f059381ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-738f-9176-512f059381ff_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019dd9a5-d910-738f-9176-512f059381ff" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-738f-9176-512f059381ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-7a70-a8f6-d5dbd888e7f8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019dd9a5-d910-738f-9176-512f059381ff" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-7a70-a8f6-d5dbd888e7f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_A2022ShareRepurchaseProgramMember_019dd9a5-d910-72c5-93eb-abcbcf5de1ab" xlink:href="tw-20260630.xsd#tw_A2022ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-7a70-a8f6-d5dbd888e7f8" xlink:to="loc_tw_A2022ShareRepurchaseProgramMember_019dd9a5-d910-72c5-93eb-abcbcf5de1ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_A2021ShareRepurchaseProgramMember_019dd9a5-d910-738f-b100-3adb7fa28c70" xlink:href="tw-20260630.xsd#tw_A2021ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-7a70-a8f6-d5dbd888e7f8" xlink:to="loc_tw_A2021ShareRepurchaseProgramMember_019dd9a5-d910-738f-b100-3adb7fa28c70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_A2026ShareRepurchaseProgramMember_019dd9a5-d910-7f8b-a82f-cce5264af2e0" xlink:href="tw-20260630.xsd#tw_A2026ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019dd9a5-d910-7a70-a8f6-d5dbd888e7f8" xlink:to="loc_tw_A2026ShareRepurchaseProgramMember_019dd9a5-d910-7f8b-a82f-cce5264af2e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7660-ba23-f6fdf945b12b" 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_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7729-9b41-b3ee66362ece" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d910-7660-ba23-f6fdf945b12b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7660-ba23-f6fdf945b12b_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_019dd9a5-d910-7660-ba23-f6fdf945b12b" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7660-ba23-f6fdf945b12b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7834-81f2-0cf066ac97ee" 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_019dd9a5-d910-7660-ba23-f6fdf945b12b" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7834-81f2-0cf066ac97ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7ae9-b492-da8b2f4c75db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7834-81f2-0cf066ac97ee" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d910-7ae9-b492-da8b2f4c75db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_OtherShareRepurchasesProgramMember_019dd9a5-d910-7616-956a-cb4b1aabd8fa" xlink:href="tw-20260630.xsd#tw_OtherShareRepurchasesProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d910-7834-81f2-0cf066ac97ee" xlink:to="loc_tw_OtherShareRepurchasesProgramMember_019dd9a5-d910-7616-956a-cb4b1aabd8fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019dd9a5-d910-79b1-ae9b-525f6b1d9aa6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019dd9a5-d910-79b1-ae9b-525f6b1d9aa6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019dd9a5-d910-7028-b1d9-4c69341db5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019dd9a5-d910-7028-b1d9-4c69341db5f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019dd9a5-d910-766e-8c75-e2ab6cbe3212" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019dd9a5-d910-766e-8c75-e2ab6cbe3212" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019dd9a5-d910-7f2a-8a2a-10c6613fbfd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019dd9a5-d910-7f2a-8a2a-10c6613fbfd0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_019dd9a5-d910-7a1e-8042-69954225131e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_019dd9a5-d910-7a1e-8042-69954225131e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformancePeriod_019dd9a5-d910-7c3b-8111-581af0ea8556" xlink:href="tw-20260630.xsd#tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformancePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformancePeriod_019dd9a5-d910-7c3b-8111-581af0ea8556" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPerformanceModifier_019dd9a5-d910-752e-871f-d630212ba9b8" xlink:href="tw-20260630.xsd#tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPerformanceModifier"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPerformanceModifier_019dd9a5-d910-752e-871f-d630212ba9b8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPerformanceModifier_019dd9a5-d910-71ed-86e2-f799c666f04d" xlink:href="tw-20260630.xsd#tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPerformanceModifier"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPerformanceModifier_019dd9a5-d910-71ed-86e2-f799c666f04d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetPerformanceModifier_019dd9a5-d910-7274-aebb-28aa1493ab8f" xlink:href="tw-20260630.xsd#tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetPerformanceModifier"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_tw_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetPerformanceModifier_019dd9a5-d910-7274-aebb-28aa1493ab8f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_019dd9a5-d910-7d4a-970f-656a29060193" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_019dd9a5-d910-7d4a-970f-656a29060193" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019dd9a5-d910-7d39-bf17-e1f78b3a0adc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019dd9a5-d910-7d39-bf17-e1f78b3a0adc" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019f1383-a2bc-7c68-a235-474ca9b323a1" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019f1383-a2bc-7c68-a235-474ca9b323a1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019dd9a5-d910-7d79-bcd1-127774be4f2f" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019dd9a5-d910-7d79-bcd1-127774be4f2f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019f138a-00d6-7d3e-ad42-161472a253ad" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019f138a-00d6-7d3e-ad42-161472a253ad" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019f617a-e6a7-78e2-b44c-f611074e3f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019f617a-e6a7-78e2-b44c-f611074e3f5e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramExciseTax_019f617f-3d77-702f-8f95-d5fba3ed9831" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareRepurchaseProgramExciseTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_ShareRepurchaseProgramExciseTax_019f617f-3d77-702f-8f95-d5fba3ed9831" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019dd9a5-d910-7fec-ba1c-db1f1dfb0426" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019dd9a5-d910-7fec-ba1c-db1f1dfb0426" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019dd9a5-d910-79a4-835d-8f06b10b7db7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7151-9438-769e89f137dc" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019dd9a5-d910-79a4-835d-8f06b10b7db7" xlink:type="arc" order="17"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/StockholdersEquityandStockBasedCompensationPlansScheduleofSignificantValuationAssumptionsUsedToEstimateTheGrantDateFairValueofPSUsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#StockholdersEquityandStockBasedCompensationPlansScheduleofSignificantValuationAssumptionsUsedToEstimateTheGrantDateFairValueofPSUsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/StockholdersEquityandStockBasedCompensationPlansScheduleofSignificantValuationAssumptionsUsedToEstimateTheGrantDateFairValueofPSUsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7f50-a931-9b8f29314636" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7ae3-a7a3-c4ddec11ff84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7f50-a931-9b8f29314636" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7ae3-a7a3-c4ddec11ff84" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-73be-ab27-7c688ca32a19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019dd9a5-d910-7ae3-a7a3-c4ddec11ff84" xlink:to="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-73be-ab27-7c688ca32a19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-73be-ab27-7c688ca32a19_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-73be-ab27-7c688ca32a19" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-73be-ab27-7c688ca32a19_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-74c9-80b0-25cdf866dbe5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019dd9a5-d910-73be-ab27-7c688ca32a19" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-74c9-80b0-25cdf866dbe5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d910-752a-8242-653b81c23252" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d910-74c9-80b0-25cdf866dbe5" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d910-752a-8242-653b81c23252" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_019dd9a5-d910-7a3c-bea0-00c9f628ebf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7f50-a931-9b8f29314636" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_019dd9a5-d910-7a3c-bea0-00c9f628ebf5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_019dd9a5-d910-7c3e-b6fb-6f7f19ce4359" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7f50-a931-9b8f29314636" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_019dd9a5-d910-7c3e-b6fb-6f7f19ce4359" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_019dd9a5-d910-7517-a791-c41ae183ada4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019dd9a5-d910-7f50-a931-9b8f29314636" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_019dd9a5-d910-7517-a791-c41ae183ada4" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/RelatedPartyTransactionsScheduleofBalancesFromTransactionswithAffiliatesIncludedintheConsolidatedStatementsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#RelatedPartyTransactionsScheduleofBalancesFromTransactionswithAffiliatesIncludedintheConsolidatedStatementsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/RelatedPartyTransactionsScheduleofBalancesFromTransactionswithAffiliatesIncludedintheConsolidatedStatementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7d62-9428-9d2a9e89fb5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7d62-9428-9d2a9e89fb5e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019dd9a5-d910-770d-b134-a962fa50d95a" 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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7d62-9428-9d2a9e89fb5e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019dd9a5-d910-770d-b134-a962fa50d95a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019dd9a5-d910-770d-b134-a962fa50d95a_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_019dd9a5-d910-770d-b134-a962fa50d95a" xlink:to="loc_us-gaap_RelatedPartyDomain_019dd9a5-d910-770d-b134-a962fa50d95a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019dd9a5-d910-77b9-ae26-8b8d7202b7e0" 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_019dd9a5-d910-770d-b134-a962fa50d95a" xlink:to="loc_us-gaap_RelatedPartyDomain_019dd9a5-d910-77b9-ae26-8b8d7202b7e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_019dd9a5-d910-724d-a770-860806dd8581" 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_019dd9a5-d910-77b9-ae26-8b8d7202b7e0" xlink:to="loc_srt_AffiliatedEntityMember_019dd9a5-d910-724d-a770-860806dd8581" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019dd9a5-d910-746a-a52f-078d2b45b224" 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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7d62-9428-9d2a9e89fb5e" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019dd9a5-d910-746a-a52f-078d2b45b224" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d910-746a-a52f-078d2b45b224_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_019dd9a5-d910-746a-a52f-078d2b45b224" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d910-746a-a52f-078d2b45b224_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d910-7e09-986a-d60c1f24c86e" 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_019dd9a5-d910-746a-a52f-078d2b45b224" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d910-7e09-986a-d60c1f24c86e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_IAltaACapitalMarketsLLCMember_019dd9a5-d910-76aa-b556-1e9252ed5109" xlink:href="tw-20260630.xsd#tw_IAltaACapitalMarketsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d910-7e09-986a-d60c1f24c86e" xlink:to="loc_tw_IAltaACapitalMarketsLLCMember_019dd9a5-d910-76aa-b556-1e9252ed5109" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_OtherEquityInvestmentsMember_019dd9a5-d910-7992-ab28-6deb3221913e" xlink:href="tw-20260630.xsd#tw_OtherEquityInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d910-7e09-986a-d60c1f24c86e" xlink:to="loc_tw_OtherEquityInvestmentsMember_019dd9a5-d910-7992-ab28-6deb3221913e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance_019dd9a5-d910-7954-9e91-05f4a2a03161" xlink:href="tw-20260630.xsd#tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance_019dd9a5-d910-7954-9e91-05f4a2a03161" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_019dd9a5-d910-76d7-8103-ff1602f97744" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_OtherReceivables_019dd9a5-d910-76d7-8103-ff1602f97744" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019dd9a5-d910-7e45-9479-f19d70f0efbe" 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_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_OtherAssets_019dd9a5-d910-7e45-9479-f19d70f0efbe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019dd9a5-d910-77ad-a901-2c50c04f7611" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019dd9a5-d910-77ad-a901-2c50c04f7611" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019dd9a5-d910-76fb-8332-b1720ec60ff6" 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_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_OtherLiabilities_019dd9a5-d910-76fb-8332-b1720ec60ff6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019dd9a5-d910-749d-8aac-be5f841adbda" 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_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_EquityMethodInvestments_019dd9a5-d910-749d-8aac-be5f841adbda" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019dd9a5-d910-7438-ba05-34afbd4ce55a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d910-70e4-b20b-5558d94b4138" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019dd9a5-d910-7438-ba05-34afbd4ce55a" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/RelatedPartyTransactionsScheduleofAffiliateswereIncludedintheConsolidatedStatementsofIncomeDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#RelatedPartyTransactionsScheduleofAffiliateswereIncludedintheConsolidatedStatementsofIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/RelatedPartyTransactionsScheduleofAffiliateswereIncludedintheConsolidatedStatementsofIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d9f0-7124-8479-a0003f4a53db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7df0-af69-4ae7eec55838" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d9f0-7124-8479-a0003f4a53db" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7df0-af69-4ae7eec55838" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019dd9a5-d910-7220-8508-31caed01261d" 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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7df0-af69-4ae7eec55838" xlink:to="loc_srt_ProductOrServiceAxis_019dd9a5-d910-7220-8508-31caed01261d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7220-8508-31caed01261d_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_019dd9a5-d910-7220-8508-31caed01261d" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-7220-8508-31caed01261d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-70ad-a251-737ffa5f8525" 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_019dd9a5-d910-7220-8508-31caed01261d" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-70ad-a251-737ffa5f8525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_SubscriptionFeeRevenueMember_019dd9a5-d910-727c-b2e1-19af6912fb88" xlink:href="tw-20260630.xsd#tw_SubscriptionFeeRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-70ad-a251-737ffa5f8525" xlink:to="loc_tw_SubscriptionFeeRevenueMember_019dd9a5-d910-727c-b2e1-19af6912fb88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MarketDataRevenueMember_019dd9a5-d910-711c-ba99-366d5076330a" xlink:href="tw-20260630.xsd#tw_MarketDataRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-70ad-a251-737ffa5f8525" xlink:to="loc_tw_MarketDataRevenueMember_019dd9a5-d910-711c-ba99-366d5076330a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d910-75ee-93c0-f5c1c49d4f8a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d910-70ad-a251-737ffa5f8525" xlink:to="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d910-75ee-93c0-f5c1c49d4f8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019dd9a5-d910-7a5a-9d79-6987e62a5068" 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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7df0-af69-4ae7eec55838" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019dd9a5-d910-7a5a-9d79-6987e62a5068" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019dd9a5-d910-7a5a-9d79-6987e62a5068_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_019dd9a5-d910-7a5a-9d79-6987e62a5068" xlink:to="loc_us-gaap_RelatedPartyDomain_019dd9a5-d910-7a5a-9d79-6987e62a5068_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019dd9a5-d9f0-7960-a2ba-628d41a214a2" 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_019dd9a5-d910-7a5a-9d79-6987e62a5068" xlink:to="loc_us-gaap_RelatedPartyDomain_019dd9a5-d9f0-7960-a2ba-628d41a214a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_019dd9a5-d9f0-7083-b180-983c51124c70" 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_019dd9a5-d9f0-7960-a2ba-628d41a214a2" xlink:to="loc_srt_AffiliatedEntityMember_019dd9a5-d9f0-7083-b180-983c51124c70" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019dd9a5-d9f0-7918-8064-d2442e12aa94" 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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019dd9a5-d910-7df0-af69-4ae7eec55838" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019dd9a5-d9f0-7918-8064-d2442e12aa94" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d9f0-7918-8064-d2442e12aa94_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_019dd9a5-d9f0-7918-8064-d2442e12aa94" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d9f0-7918-8064-d2442e12aa94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d9f0-7e41-9e41-eacf04042fcc" 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_019dd9a5-d9f0-7918-8064-d2442e12aa94" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d9f0-7e41-9e41-eacf04042fcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_IAltaACapitalMarketsLLCMember_019dd9a5-d9f0-7f54-a954-97920eb0df36" xlink:href="tw-20260630.xsd#tw_IAltaACapitalMarketsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d9f0-7e41-9e41-eacf04042fcc" xlink:to="loc_tw_IAltaACapitalMarketsLLCMember_019dd9a5-d9f0-7f54-a954-97920eb0df36" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MAXEXLLCMember_019dd9a5-d9f0-774e-806b-01e363534ff5" xlink:href="tw-20260630.xsd#tw_MAXEXLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019dd9a5-d9f0-7e41-9e41-eacf04042fcc" xlink:to="loc_tw_MAXEXLLCMember_019dd9a5-d9f0-774e-806b-01e363534ff5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019dd9a5-d9f0-7278-bc85-7829a7692f69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d9f0-7124-8479-a0003f4a53db" xlink:to="loc_us-gaap_RevenuesAbstract_019dd9a5-d9f0-7278-bc85-7829a7692f69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f0-7dfa-b17d-ee76229d8c92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019dd9a5-d9f0-7278-bc85-7829a7692f69" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f0-7dfa-b17d-ee76229d8c92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d9f0-7124-8479-a0003f4a53db" xlink:to="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019dd9a5-d9f0-79ae-8f79-7261a8546797" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019dd9a5-d9f0-79ae-8f79-7261a8546797" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_019dd9a5-d9f0-71a5-8e14-0d9a27862b40" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommunicationsAndInformationTechnology"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_019dd9a5-d9f0-71a5-8e14-0d9a27862b40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_OtherGeneralAndAdministrativeExpenseNetOfReclassification_019dd9a5-d9f0-72c1-ac2d-f0f486dce87e" xlink:href="tw-20260630.xsd#tw_OtherGeneralAndAdministrativeExpenseNetOfReclassification"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:to="loc_tw_OtherGeneralAndAdministrativeExpenseNetOfReclassification_019dd9a5-d9f0-72c1-ac2d-f0f486dce87e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019dd9a5-d9f0-7d3b-9c59-1f448a2954a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:to="loc_us-gaap_ProfessionalFees_019dd9a5-d9f0-7d3b-9c59-1f448a2954a7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_019dd9a5-d9f0-73bd-9367-4afca7667ffa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OccupancyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:to="loc_us-gaap_OccupancyNet_019dd9a5-d9f0-73bd-9367-4afca7667ffa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019dd9a5-d9f0-736e-b77f-7bf9445b8e81" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestIncomeSecuritiesOperatingByTaxableStatusAbstract_019dd9a5-d9f0-79c4-9d7f-dff9f0ed0c53" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019dd9a5-d9f0-736e-b77f-7bf9445b8e81" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019dd9a5-d9f0-7588-8fe3-f661ef7a403a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019dd9a5-d9f0-7124-8479-a0003f4a53db" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019dd9a5-d9f0-7588-8fe3-f661ef7a403a" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofFinancialInstrumentsMeasuredatFairValueDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofFinancialInstrumentsMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofFinancialInstrumentsMeasuredatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" 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_019dd9a5-d9f0-7d8a-b443-c93a32724427" 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_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d8a-b443-c93a32724427" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019dd9a5-d9f0-7c55-9b1e-d7165920dbcc" 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_019dd9a5-d9f0-7d8a-b443-c93a32724427" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019dd9a5-d9f0-7c55-9b1e-d7165920dbcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7c55-9b1e-d7165920dbcc_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_019dd9a5-d9f0-7c55-9b1e-d7165920dbcc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7c55-9b1e-d7165920dbcc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7d12-a8d2-ec9f30a5db07" 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_019dd9a5-d9f0-7c55-9b1e-d7165920dbcc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7d12-a8d2-ec9f30a5db07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019dd9a5-d9f0-70ff-be08-27b4aa5b8c2c" 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_019dd9a5-d9f0-7d12-a8d2-ec9f30a5db07" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019dd9a5-d9f0-70ff-be08-27b4aa5b8c2c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019dd9a5-d9f0-70cb-9034-5fd0cb4fb693" 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_019dd9a5-d9f0-7d12-a8d2-ec9f30a5db07" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019dd9a5-d9f0-70cb-9034-5fd0cb4fb693" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019dd9a5-d9f0-7157-8646-01c4537b3aa3" 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_019dd9a5-d9f0-7d12-a8d2-ec9f30a5db07" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019dd9a5-d9f0-7157-8646-01c4537b3aa3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019dd9a5-d9f0-7cbf-b5d9-2e3bcaad7d3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019dd9a5-d9f0-7cbf-b5d9-2e3bcaad7d3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019dd9a5-d9f0-7725-8ba7-23e21da8d64c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019dd9a5-d9f0-7725-8ba7-23e21da8d64c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019dd9a5-d9f0-7c5d-b2a0-e33589a4d5f7" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019dd9a5-d9f0-7c5d-b2a0-e33589a4d5f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_019dd9a5-d9f0-73a0-8f8e-d821a03fb652" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_019dd9a5-d9f0-73a0-8f8e-d821a03fb652" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetFairValue_019dd9a5-d9f0-7880-ac8b-d4cedb83f7ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_CryptoAssetFairValue_019dd9a5-d9f0-7880-ac8b-d4cedb83f7ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019dd9a5-d9f0-7f92-964c-c26a0e738d7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_DerivativeAssets_019dd9a5-d9f0-7f92-964c-c26a0e738d7c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019dd9a5-d9f0-77d2-8ee0-e6085cbf75de" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019dd9a5-d9f0-77d2-8ee0-e6085cbf75de" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019dd9a5-d9f0-7157-877e-ec688cfcb526" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_DerivativeLiabilities_019dd9a5-d9f0-7157-877e-ec688cfcb526" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019dd9a5-d9f0-7df4-a98e-0e7f47a4177a" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7115-90d1-1086659b52c7" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019dd9a5-d9f0-7df4-a98e-0e7f47a4177a" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsNarrativeDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" 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_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" 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_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7d21-aafe-504a71e93ffe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7d21-aafe-504a71e93ffe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-707e-8af4-8078c506aa50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-707e-8af4-8078c506aa50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleNotesPayableMember_019dd9a5-d9f0-7876-b14b-17860be5d299" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleNotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-707e-8af4-8078c506aa50" xlink:to="loc_us-gaap_ConvertibleNotesPayableMember_019dd9a5-d9f0-7876-b14b-17860be5d299" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_019dd9a5-d9f0-7568-9b05-c19ee6eee544" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_019dd9a5-d9f0-7568-9b05-c19ee6eee544" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7568-9b05-c19ee6eee544_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_019dd9a5-d9f0-7568-9b05-c19ee6eee544" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7568-9b05-c19ee6eee544_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" 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_019dd9a5-d9f0-7568-9b05-c19ee6eee544" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_019dd9a5-d9f0-7085-b364-3a97e4aed787" 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_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_019dd9a5-d9f0-7085-b364-3a97e4aed787" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MeasurementInputPerpetualGrowthRateMember_019e45f7-5815-737b-a941-2575111fb9ff" xlink:href="tw-20260630.xsd#tw_MeasurementInputPerpetualGrowthRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" xlink:to="loc_tw_MeasurementInputPerpetualGrowthRateMember_019e45f7-5815-737b-a941-2575111fb9ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7d15-b0e4-40b6501df177_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7d15-b0e4-40b6501df177_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7483-8ef1-2284509fba17" xlink:href="tw-20260630.xsd#tw_CantonCoinsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:to="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7483-8ef1-2284509fba17" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DigitalAssetLoanReceivableMember_019dd9a5-d9f0-764e-acea-ebb5fef36cd8" xlink:href="tw-20260630.xsd#tw_DigitalAssetLoanReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:to="loc_tw_DigitalAssetLoanReceivableMember_019dd9a5-d9f0-764e-acea-ebb5fef36cd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_019dd9a5-d9f0-731b-b061-e17a4b8b1959" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfFinancialPositionLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_019dd9a5-d9f0-731b-b061-e17a4b8b1959" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-7c77-b159-da0e63b9bb53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-7c77-b159-da0e63b9bb53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_PreFundedWarrantsMember_019dd9a5-d9f0-7575-b262-dd9296ec06d3" xlink:href="tw-20260630.xsd#tw_PreFundedWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-7c77-b159-da0e63b9bb53" xlink:to="loc_tw_PreFundedWarrantsMember_019dd9a5-d9f0-7575-b262-dd9296ec06d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_srt_ProductOrServiceAxis_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5_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_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a96-aec9-6004b63684fa" 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_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a96-aec9-6004b63684fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d9f0-7ea4-8cb4-86e78b03608d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a96-aec9-6004b63684fa" xlink:to="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d9f0-7ea4-8cb4-86e78b03608d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e45f7-5815-7ffc-82b1-0e668bab4cac" 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_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e45f7-5815-7ffc-82b1-0e668bab4cac" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7ffc-82b1-0e668bab4cac_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_019e45f7-5815-7ffc-82b1-0e668bab4cac" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7ffc-82b1-0e668bab4cac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7980-b945-4e7094f079b6" 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_019e45f7-5815-7ffc-82b1-0e668bab4cac" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7980-b945-4e7094f079b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e45f7-5815-7cf9-8600-fa31d5e6a94b" 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_019e45f7-5815-7980-b945-4e7094f079b6" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e45f7-5815-7cf9-8600-fa31d5e6a94b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019f3d0d-6664-76fd-87c7-1c4048546e3b" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019f3d0d-6664-76fd-87c7-1c4048546e3b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-76fd-87c7-1c4048546e3b_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_019f3d0d-6664-76fd-87c7-1c4048546e3b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-76fd-87c7-1c4048546e3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-7f2e-a6f0-e971717f5d88" 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_019f3d0d-6664-76fd-87c7-1c4048546e3b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-7f2e-a6f0-e971717f5d88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019f3d0d-8fc3-713f-885c-6a4ef397ee69" 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_019f3d0d-6664-7f2e-a6f0-e971717f5d88" xlink:to="loc_us-gaap_SubsequentEventMember_019f3d0d-8fc3-713f-885c-6a4ef397ee69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019f4373-3894-7755-b4e9-d761847064f3" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019f4373-3894-7755-b4e9-d761847064f3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-7755-b4e9-d761847064f3_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_019f4373-3894-7755-b4e9-d761847064f3" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-7755-b4e9-d761847064f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-726f-ab81-3054c81139a6" 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_019f4373-3894-7755-b4e9-d761847064f3" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-726f-ab81-3054c81139a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_019f4373-60b3-7eb8-9513-3ee007276f95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-726f-ab81-3054c81139a6" xlink:to="loc_us-gaap_DebtSecuritiesMember_019f4373-60b3-7eb8-9513-3ee007276f95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019dd9a5-d9f0-76cd-bb5d-fd29cbc10a2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019dd9a5-d9f0-76cd-bb5d-fd29cbc10a2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019dd9a5-d9f0-73dd-9071-c9533afe74e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019dd9a5-d9f0-73dd-9071-c9533afe74e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPreacquisitionEstimatedValue_019dd9a5-d9f0-7906-8ef9-8a1b9d13c4e5" xlink:href="tw-20260630.xsd#tw_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPreacquisitionEstimatedValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPreacquisitionEstimatedValue_019dd9a5-d9f0-7906-8ef9-8a1b9d13c4e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_019f618d-ec91-7125-9a43-c5aec9d1bb4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_019f618d-ec91-7125-9a43-c5aec9d1bb4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019dd9a5-d9f0-7db0-a8f3-0107f260cd09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019dd9a5-d9f0-7db0-a8f3-0107f260cd09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded_019dd9a5-d9f0-7ecf-860f-8a2a4096ccc1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded_019dd9a5-d9f0-7ecf-860f-8a2a4096ccc1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019dd9a5-d9f0-77ee-b337-41dead4a37b6" 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_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019dd9a5-d9f0-77ee-b337-41dead4a37b6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f0-7fbd-88be-123f9f7da45d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f0-7fbd-88be-123f9f7da45d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019dd9a5-d9f0-78d5-a2c9-3513f3beba43" 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_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019dd9a5-d9f0-78d5-a2c9-3513f3beba43" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CryptoAssetSaleNumberOfUnits_019dd9a5-d9f0-7d0b-b9b5-88f7b46a8571" xlink:href="tw-20260630.xsd#tw_CryptoAssetSaleNumberOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_CryptoAssetSaleNumberOfUnits_019dd9a5-d9f0-7d0b-b9b5-88f7b46a8571" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_019dd9a5-d9f0-7644-8d56-5f823749f2da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_019dd9a5-d9f0-7644-8d56-5f823749f2da" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstanding_019dd9a5-d9f0-7add-8986-f1f47f3ea383" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantsAndRightsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_WarrantsAndRightsOutstanding_019dd9a5-d9f0-7add-8986-f1f47f3ea383" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetRealizedGainNonoperating_019dd9a5-d9f0-704c-9c8e-a7d0913b32cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedGainNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_CryptoAssetRealizedGainNonoperating_019dd9a5-d9f0-704c-9c8e-a7d0913b32cb" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CryptoAssetLoanReceivable_019dd9a5-d9f0-7c23-94ce-640ef3aeb2a7" xlink:href="tw-20260630.xsd#tw_CryptoAssetLoanReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_CryptoAssetLoanReceivable_019dd9a5-d9f0-7c23-94ce-640ef3aeb2a7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_019dd9a5-d9f0-7dea-99fd-51bc7a996c54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_019dd9a5-d9f0-7dea-99fd-51bc7a996c54" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d9f0-714c-8222-57b0532c49c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d9f0-714c-8222-57b0532c49c1" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019dd9a5-d9f0-7569-8ef3-2639e8fd5edd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019dd9a5-d9f0-7569-8ef3-2639e8fd5edd" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ClassOfWarrantOrRightExercised_019e498d-2e7e-776b-92a8-6178c8db9c07" xlink:href="tw-20260630.xsd#tw_ClassOfWarrantOrRightExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_ClassOfWarrantOrRightExercised_019e498d-2e7e-776b-92a8-6178c8db9c07" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019dd9a5-d9f0-7ccc-a293-a3c0645bd103" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019dd9a5-d9f0-7ccc-a293-a3c0645bd103" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019dd9a5-d9f0-7a69-bb34-1d05d55c61e1" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquityMethodInvestments_019dd9a5-d9f0-7a69-bb34-1d05d55c61e1" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySecuritiesUnfundedCapitalCommitment_019dd9a5-d9f0-764c-895e-91793f030d62" xlink:href="tw-20260630.xsd#tw_EquitySecuritiesUnfundedCapitalCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_EquitySecuritiesUnfundedCapitalCommitment_019dd9a5-d9f0-764c-895e-91793f030d62" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019dd9a5-d9f0-7e58-b612-859d685e47fb" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019dd9a5-d9f0-7e58-b612-859d685e47fb" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019dd9a5-d9f0-7955-866b-085a05bdddc6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019dd9a5-d9f0-7955-866b-085a05bdddc6" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019dd9a5-d9f0-7e8f-9171-ab0cec457fe6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019dd9a5-d9f0-7e8f-9171-ab0cec457fe6" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_019e4985-8d3a-7510-a518-df90e44b0423" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_019e4985-8d3a-7510-a518-df90e44b0423" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount_019dd9a5-d9f0-7aa5-85a8-fa7c3c6de5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount_019dd9a5-d9f0-7aa5-85a8-fa7c3c6de5f7" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySecuritiesWithoutReadilyDeterminableFairValueMeasurementInput_019e45f7-5815-7d78-a56d-4ca39a37fc78" xlink:href="tw-20260630.xsd#tw_EquitySecuritiesWithoutReadilyDeterminableFairValueMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_EquitySecuritiesWithoutReadilyDeterminableFairValueMeasurementInput_019e45f7-5815-7d78-a56d-4ca39a37fc78" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount_019dd9a5-d9f0-78bd-9263-25af254a30b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount_019dd9a5-d9f0-78bd-9263-25af254a30b1" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount_019dd9a5-d9f0-7d88-8234-7d844eb8f0ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount_019dd9a5-d9f0-7d88-8234-7d844eb8f0ce" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsNarrativeDetails_1" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsNarrativeDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" 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_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" 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_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7d21-aafe-504a71e93ffe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7d21-aafe-504a71e93ffe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-707e-8af4-8078c506aa50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-7d21-aafe-504a71e93ffe" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-707e-8af4-8078c506aa50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleNotesPayableMember_019dd9a5-d9f0-7876-b14b-17860be5d299" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleNotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-707e-8af4-8078c506aa50" xlink:to="loc_us-gaap_ConvertibleNotesPayableMember_019dd9a5-d9f0-7876-b14b-17860be5d299" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_019dd9a5-d9f0-7568-9b05-c19ee6eee544" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_019dd9a5-d9f0-7568-9b05-c19ee6eee544" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7568-9b05-c19ee6eee544_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_019dd9a5-d9f0-7568-9b05-c19ee6eee544" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7568-9b05-c19ee6eee544_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" 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_019dd9a5-d9f0-7568-9b05-c19ee6eee544" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_019dd9a5-d9f0-7085-b364-3a97e4aed787" 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_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_019dd9a5-d9f0-7085-b364-3a97e4aed787" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MeasurementInputPerpetualGrowthRateMember_019e45f7-5815-737b-a941-2575111fb9ff" xlink:href="tw-20260630.xsd#tw_MeasurementInputPerpetualGrowthRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019dd9a5-d9f0-7c29-9c64-f966c3c2c9f5" xlink:to="loc_tw_MeasurementInputPerpetualGrowthRateMember_019e45f7-5815-737b-a941-2575111fb9ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7d15-b0e4-40b6501df177_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7d15-b0e4-40b6501df177_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7d15-b0e4-40b6501df177" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7483-8ef1-2284509fba17" xlink:href="tw-20260630.xsd#tw_CantonCoinsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:to="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7483-8ef1-2284509fba17" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DigitalAssetLoanReceivableMember_019dd9a5-d9f0-764e-acea-ebb5fef36cd8" xlink:href="tw-20260630.xsd#tw_DigitalAssetLoanReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-765a-9df4-5d102cbcacd0" xlink:to="loc_tw_DigitalAssetLoanReceivableMember_019dd9a5-d9f0-764e-acea-ebb5fef36cd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-7c77-b159-da0e63b9bb53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019dd9a5-d9f0-73ad-91ae-a81b2203e3c6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-7c77-b159-da0e63b9bb53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_PreFundedWarrantsMember_019dd9a5-d9f0-7575-b262-dd9296ec06d3" xlink:href="tw-20260630.xsd#tw_PreFundedWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019dd9a5-d9f0-7c77-b159-da0e63b9bb53" xlink:to="loc_tw_PreFundedWarrantsMember_019dd9a5-d9f0-7575-b262-dd9296ec06d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_srt_ProductOrServiceAxis_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5_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_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a96-aec9-6004b63684fa" 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_019dd9a5-d9f0-7a54-af3c-2260b79fe4b5" xlink:to="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a96-aec9-6004b63684fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d9f0-7ea4-8cb4-86e78b03608d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019dd9a5-d9f0-7a96-aec9-6004b63684fa" xlink:to="loc_us-gaap_FinancialServiceOtherMember_019dd9a5-d9f0-7ea4-8cb4-86e78b03608d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e45f7-5815-7ffc-82b1-0e668bab4cac" 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_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e45f7-5815-7ffc-82b1-0e668bab4cac" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7ffc-82b1-0e668bab4cac_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_019e45f7-5815-7ffc-82b1-0e668bab4cac" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7ffc-82b1-0e668bab4cac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7980-b945-4e7094f079b6" 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_019e45f7-5815-7ffc-82b1-0e668bab4cac" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e45f7-5815-7980-b945-4e7094f079b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e45f7-5815-7cf9-8600-fa31d5e6a94b" 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_019e45f7-5815-7980-b945-4e7094f079b6" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e45f7-5815-7cf9-8600-fa31d5e6a94b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019f3d0d-6664-76fd-87c7-1c4048546e3b" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019f3d0d-6664-76fd-87c7-1c4048546e3b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-76fd-87c7-1c4048546e3b_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_019f3d0d-6664-76fd-87c7-1c4048546e3b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-76fd-87c7-1c4048546e3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-7f2e-a6f0-e971717f5d88" 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_019f3d0d-6664-76fd-87c7-1c4048546e3b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019f3d0d-6664-7f2e-a6f0-e971717f5d88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019f3d0d-8fc3-713f-885c-6a4ef397ee69" 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_019f3d0d-6664-7f2e-a6f0-e971717f5d88" xlink:to="loc_us-gaap_SubsequentEventMember_019f3d0d-8fc3-713f-885c-6a4ef397ee69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019f4373-3894-7755-b4e9-d761847064f3" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7d6b-975b-b4abcb69a3c0" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019f4373-3894-7755-b4e9-d761847064f3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-7755-b4e9-d761847064f3_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_019f4373-3894-7755-b4e9-d761847064f3" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-7755-b4e9-d761847064f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-726f-ab81-3054c81139a6" 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_019f4373-3894-7755-b4e9-d761847064f3" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-726f-ab81-3054c81139a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_019f4373-60b3-7eb8-9513-3ee007276f95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019f4373-3894-726f-ab81-3054c81139a6" xlink:to="loc_us-gaap_DebtSecuritiesMember_019f4373-60b3-7eb8-9513-3ee007276f95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019dd9a5-d9f0-76cd-bb5d-fd29cbc10a2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019dd9a5-d9f0-76cd-bb5d-fd29cbc10a2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019dd9a5-d9f0-73dd-9071-c9533afe74e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019dd9a5-d9f0-73dd-9071-c9533afe74e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPreacquisitionEstimatedValue_019dd9a5-d9f0-7906-8ef9-8a1b9d13c4e5" xlink:href="tw-20260630.xsd#tw_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPreacquisitionEstimatedValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPreacquisitionEstimatedValue_019dd9a5-d9f0-7906-8ef9-8a1b9d13c4e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_019f618d-ec91-7125-9a43-c5aec9d1bb4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_019f618d-ec91-7125-9a43-c5aec9d1bb4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019dd9a5-d9f0-7db0-a8f3-0107f260cd09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019dd9a5-d9f0-7db0-a8f3-0107f260cd09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded_019dd9a5-d9f0-7ecf-860f-8a2a4096ccc1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded_019dd9a5-d9f0-7ecf-860f-8a2a4096ccc1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019dd9a5-d9f0-77ee-b337-41dead4a37b6" 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_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019dd9a5-d9f0-77ee-b337-41dead4a37b6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f0-7fbd-88be-123f9f7da45d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f0-7fbd-88be-123f9f7da45d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019dd9a5-d9f0-78d5-a2c9-3513f3beba43" 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_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019dd9a5-d9f0-78d5-a2c9-3513f3beba43" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CryptoAssetSaleNumberOfUnits_019dd9a5-d9f0-7d0b-b9b5-88f7b46a8571" xlink:href="tw-20260630.xsd#tw_CryptoAssetSaleNumberOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_CryptoAssetSaleNumberOfUnits_019dd9a5-d9f0-7d0b-b9b5-88f7b46a8571" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_019dd9a5-d9f0-7644-8d56-5f823749f2da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_019dd9a5-d9f0-7644-8d56-5f823749f2da" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstanding_019dd9a5-d9f0-7add-8986-f1f47f3ea383" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantsAndRightsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_WarrantsAndRightsOutstanding_019dd9a5-d9f0-7add-8986-f1f47f3ea383" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetRealizedGainNonoperating_019dd9a5-d9f0-704c-9c8e-a7d0913b32cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedGainNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_CryptoAssetRealizedGainNonoperating_019dd9a5-d9f0-704c-9c8e-a7d0913b32cb" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CryptoAssetLoanReceivable_019dd9a5-d9f0-7c23-94ce-640ef3aeb2a7" xlink:href="tw-20260630.xsd#tw_CryptoAssetLoanReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_CryptoAssetLoanReceivable_019dd9a5-d9f0-7c23-94ce-640ef3aeb2a7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_019dd9a5-d9f0-7dea-99fd-51bc7a996c54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_019dd9a5-d9f0-7dea-99fd-51bc7a996c54" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d9f0-714c-8222-57b0532c49c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d9f0-714c-8222-57b0532c49c1" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019dd9a5-d9f0-7569-8ef3-2639e8fd5edd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019dd9a5-d9f0-7569-8ef3-2639e8fd5edd" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ClassOfWarrantOrRightExercised_019e498d-2e7e-776b-92a8-6178c8db9c07" xlink:href="tw-20260630.xsd#tw_ClassOfWarrantOrRightExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_ClassOfWarrantOrRightExercised_019e498d-2e7e-776b-92a8-6178c8db9c07" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019dd9a5-d9f0-7ccc-a293-a3c0645bd103" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019dd9a5-d9f0-7ccc-a293-a3c0645bd103" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019dd9a5-d9f0-7a69-bb34-1d05d55c61e1" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquityMethodInvestments_019dd9a5-d9f0-7a69-bb34-1d05d55c61e1" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySecuritiesUnfundedCapitalCommitment_019dd9a5-d9f0-764c-895e-91793f030d62" xlink:href="tw-20260630.xsd#tw_EquitySecuritiesUnfundedCapitalCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_EquitySecuritiesUnfundedCapitalCommitment_019dd9a5-d9f0-764c-895e-91793f030d62" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019dd9a5-d9f0-7e58-b612-859d685e47fb" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019dd9a5-d9f0-7e58-b612-859d685e47fb" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019dd9a5-d9f0-7955-866b-085a05bdddc6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019dd9a5-d9f0-7955-866b-085a05bdddc6" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019dd9a5-d9f0-7e8f-9171-ab0cec457fe6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019dd9a5-d9f0-7e8f-9171-ab0cec457fe6" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_019e4985-8d3a-7510-a518-df90e44b0423" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_019e4985-8d3a-7510-a518-df90e44b0423" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount_019dd9a5-d9f0-7aa5-85a8-fa7c3c6de5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount_019dd9a5-d9f0-7aa5-85a8-fa7c3c6de5f7" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySecuritiesWithoutReadilyDeterminableFairValueMeasurementInput_019e45f7-5815-7d78-a56d-4ca39a37fc78" xlink:href="tw-20260630.xsd#tw_EquitySecuritiesWithoutReadilyDeterminableFairValueMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_tw_EquitySecuritiesWithoutReadilyDeterminableFairValueMeasurementInput_019e45f7-5815-7d78-a56d-4ca39a37fc78" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount_019dd9a5-d9f0-78bd-9263-25af254a30b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount_019dd9a5-d9f0-78bd-9263-25af254a30b1" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount_019dd9a5-d9f0-7d88-8234-7d844eb8f0ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7b4e-ad89-6420595c928c" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount_019dd9a5-d9f0-7d88-8234-7d844eb8f0ce" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofCantonCoinDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofCantonCoinDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofCantonCoinDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetHoldingTable_019dd9a5-d9f0-793b-91a4-88c78b303052" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:to="loc_us-gaap_CryptoAssetHoldingTable_019dd9a5-d9f0-793b-91a4-88c78b303052" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-74bc-9a14-8260159d0400" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CryptoAssetHoldingTable_019dd9a5-d9f0-793b-91a4-88c78b303052" xlink:to="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-74bc-9a14-8260159d0400" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-74bc-9a14-8260159d0400_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-74bc-9a14-8260159d0400" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-74bc-9a14-8260159d0400_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7ad9-896a-ceda9d65aac8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-74bc-9a14-8260159d0400" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7ad9-896a-ceda9d65aac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7633-b9cf-48a52506ed4e" xlink:href="tw-20260630.xsd#tw_CantonCoinsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7ad9-896a-ceda9d65aac8" xlink:to="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7633-b9cf-48a52506ed4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetNumberOfUnits_019dd9a5-d9f0-7027-b809-065ee9fd6363" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetNumberOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:to="loc_us-gaap_CryptoAssetNumberOfUnits_019dd9a5-d9f0-7027-b809-065ee9fd6363" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetCost_019dd9a5-d9f0-764c-bc4c-fd6a7d254bee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:to="loc_us-gaap_CryptoAssetCost_019dd9a5-d9f0-764c-bc4c-fd6a7d254bee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetFairValue_019dd9a5-d9f0-73a1-91aa-f5449a9663fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:to="loc_us-gaap_CryptoAssetFairValue_019dd9a5-d9f0-73a1-91aa-f5449a9663fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetNumberOfRestrictedUnits_019ea6c3-d85b-76e8-b9c8-3bfa04e8208b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetNumberOfRestrictedUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:to="loc_us-gaap_CryptoAssetNumberOfRestrictedUnits_019ea6c3-d85b-76e8-b9c8-3bfa04e8208b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CryptoAssetFairValueRestricted_019ea6c3-069a-7206-afe0-21fcf88c92b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValueRestricted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CryptoAssetHoldingLineItems_019dd9a5-d9f0-7f94-9939-0258a806e3a9" xlink:to="loc_us-gaap_CryptoAssetFairValueRestricted_019ea6c3-069a-7206-afe0-21fcf88c92b9" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofChangesinFairValueforLevel3Details" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofChangesinFairValueforLevel3Details"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofChangesinFairValueforLevel3Details" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019dd9a5-d9f0-7d10-b92c-24edc6c2aa86" 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_019dd9a5-d9f0-7848-a922-6f0459ec8717" 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_019dd9a5-d9f0-7d10-b92c-24edc6c2aa86" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019dd9a5-d9f0-7848-a922-6f0459ec8717" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019dd9a5-d9f0-7798-919c-76c48c03d8e4" 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_019dd9a5-d9f0-7848-a922-6f0459ec8717" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019dd9a5-d9f0-7798-919c-76c48c03d8e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019dd9a5-d9f0-7798-919c-76c48c03d8e4_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_019dd9a5-d9f0-7798-919c-76c48c03d8e4" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019dd9a5-d9f0-7798-919c-76c48c03d8e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019dd9a5-d9f0-70cf-b646-b4b6db306a43" 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_019dd9a5-d9f0-7798-919c-76c48c03d8e4" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019dd9a5-d9f0-70cf-b646-b4b6db306a43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_019dd9a5-d9f0-708b-abe3-276247924d0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019dd9a5-d9f0-70cf-b646-b4b6db306a43" xlink:to="loc_us-gaap_DebtSecuritiesMember_019dd9a5-d9f0-708b-abe3-276247924d0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-79a7-9cde-27daeabb2802" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019dd9a5-d9f0-7848-a922-6f0459ec8717" xlink:to="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-79a7-9cde-27daeabb2802" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-79a7-9cde-27daeabb2802_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-79a7-9cde-27daeabb2802" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-79a7-9cde-27daeabb2802_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-762d-884c-2b1a253caf0b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-79a7-9cde-27daeabb2802" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-762d-884c-2b1a253caf0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7ccd-957a-d49bb7e5be40" xlink:href="tw-20260630.xsd#tw_CantonCoinsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-762d-884c-2b1a253caf0b" xlink:to="loc_tw_CantonCoinsMember_019dd9a5-d9f0-7ccd-957a-d49bb7e5be40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019dd9a5-d9f0-728c-b904-543f6cdc6010" 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_019dd9a5-d9f0-7d10-b92c-24edc6c2aa86" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019dd9a5-d9f0-74c3-98c4-60ed1f7decaa" 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_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019dd9a5-d9f0-74c3-98c4-60ed1f7decaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_019e45fc-29fe-76be-803a-f5dfff251684" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_019e45fc-29fe-76be-803a-f5dfff251684" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019dd9a5-d9f0-7753-a656-c95d3e197e2e" 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_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019dd9a5-d9f0-7753-a656-c95d3e197e2e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019dd9a5-d9f0-7c6c-8a42-59986e4a253a" 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_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019dd9a5-d9f0-7c6c-8a42-59986e4a253a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019dd9a5-d9f0-7d1f-9867-eb5255521212" 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_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019dd9a5-d9f0-7d1f-9867-eb5255521212" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019dd9a5-d9f0-73b3-91bc-dc421cadbc17" 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_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019dd9a5-d9f0-728c-b904-543f6cdc6010" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019dd9a5-d9f0-73b3-91bc-dc421cadbc17" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019dd9a5-d9f0-728b-a9a9-2523f8421748" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofForeignCurrencyForwardContractsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofForeignCurrencyForwardContractsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofForeignCurrencyForwardContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-77ba-8671-e9d94af5e448" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-70e5-ada5-c31b7bb47179" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-77ba-8671-e9d94af5e448" xlink:to="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-70e5-ada5-c31b7bb47179" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d9f0-7cd9-9b25-bd7909056af4" 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_DerivativeTable_019dd9a5-d9f0-70e5-ada5-c31b7bb47179" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d9f0-7cd9-9b25-bd7909056af4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-7cd9-9b25-bd7909056af4_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_019dd9a5-d9f0-7cd9-9b25-bd7909056af4" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-7cd9-9b25-bd7909056af4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-7d6c-869a-b81d7c978a0e" 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_019dd9a5-d9f0-7cd9-9b25-bd7909056af4" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-7d6c-869a-b81d7c978a0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d9f0-74fe-b920-e7d8de01ae26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-7d6c-869a-b81d7c978a0e" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d9f0-74fe-b920-e7d8de01ae26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019dd9a5-d9f0-74c8-b3d6-8fe9b92dc683" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-70e5-ada5-c31b7bb47179" xlink:to="loc_us-gaap_HedgingDesignationAxis_019dd9a5-d9f0-74c8-b3d6-8fe9b92dc683" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019dd9a5-d9f0-74c8-b3d6-8fe9b92dc683_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019dd9a5-d9f0-74c8-b3d6-8fe9b92dc683" xlink:to="loc_us-gaap_HedgingDesignationDomain_019dd9a5-d9f0-74c8-b3d6-8fe9b92dc683_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019dd9a5-d9f0-7299-a81f-8b430f8cce32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019dd9a5-d9f0-74c8-b3d6-8fe9b92dc683" xlink:to="loc_us-gaap_HedgingDesignationDomain_019dd9a5-d9f0-7299-a81f-8b430f8cce32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019dd9a5-d9f0-7dcc-ab21-70d4d4e0fc7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019dd9a5-d9f0-7299-a81f-8b430f8cce32" xlink:to="loc_us-gaap_NondesignatedMember_019dd9a5-d9f0-7dcc-ab21-70d4d4e0fc7a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019dd9a5-d9f0-7158-ac5e-a0fb83e79a72" 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_DerivativeLineItems_019dd9a5-d9f0-77ba-8671-e9d94af5e448" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019dd9a5-d9f0-7158-ac5e-a0fb83e79a72" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofUnrealizedGainsLossesonForeignCurrencyForwardsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofUnrealizedGainsLossesonForeignCurrencyForwardsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofUnrealizedGainsLossesonForeignCurrencyForwardsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-7cfd-a7a7-3a1c6d61cedb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-7cfd-a7a7-3a1c6d61cedb" xlink:to="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d9f0-783e-b30d-cf990bd01943" 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_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d9f0-783e-b30d-cf990bd01943" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-783e-b30d-cf990bd01943_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_019dd9a5-d9f0-783e-b30d-cf990bd01943" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-783e-b30d-cf990bd01943_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-74ba-b1cb-3f8725aa12e2" 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_019dd9a5-d9f0-783e-b30d-cf990bd01943" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-74ba-b1cb-3f8725aa12e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d9f0-7674-aedf-55e90e1ee43a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-74ba-b1cb-3f8725aa12e2" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d9f0-7674-aedf-55e90e1ee43a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019dd9a5-d9f0-7775-aecf-bd43ad9a8f18" 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_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019dd9a5-d9f0-7775-aecf-bd43ad9a8f18" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d9f0-74f6-bb88-2b5e622418dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-7cfd-a7a7-3a1c6d61cedb" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d9f0-74f6-bb88-2b5e622418dd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofUnrealizedGainsLossesonForeignCurrencyForwardsDetails_1" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofUnrealizedGainsLossesonForeignCurrencyForwardsDetails_1"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofUnrealizedGainsLossesonForeignCurrencyForwardsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-7cfd-a7a7-3a1c6d61cedb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-7cfd-a7a7-3a1c6d61cedb" xlink:to="loc_us-gaap_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d9f0-783e-b30d-cf990bd01943" 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_DerivativeTable_019dd9a5-d9f0-722c-a118-262958f87b3b" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019dd9a5-d9f0-783e-b30d-cf990bd01943" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-783e-b30d-cf990bd01943_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_019dd9a5-d9f0-783e-b30d-cf990bd01943" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-783e-b30d-cf990bd01943_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-74ba-b1cb-3f8725aa12e2" 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_019dd9a5-d9f0-783e-b30d-cf990bd01943" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-74ba-b1cb-3f8725aa12e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d9f0-7674-aedf-55e90e1ee43a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019dd9a5-d9f0-74ba-b1cb-3f8725aa12e2" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019dd9a5-d9f0-7674-aedf-55e90e1ee43a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d9f0-74f6-bb88-2b5e622418dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019dd9a5-d9f0-7cfd-a7a7-3a1c6d61cedb" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019dd9a5-d9f0-74f6-bb88-2b5e622418dd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofFinancialInstrumentsNotMeasuredatFairValueDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#FairValueofFinancialInstrumentsandOtherAssetsScheduleofFinancialInstrumentsNotMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/FairValueofFinancialInstrumentsandOtherAssetsScheduleofFinancialInstrumentsNotMeasuredatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019dd9a5-d9f0-7282-9a7e-ea1350664f3d" 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_019dd9a5-d9f0-7cc3-9963-4bdee9db7df6" 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_019dd9a5-d9f0-7282-9a7e-ea1350664f3d" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7cc3-9963-4bdee9db7df6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019dd9a5-d9f0-7647-9e9f-cce1078d5c78" 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_019dd9a5-d9f0-7cc3-9963-4bdee9db7df6" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019dd9a5-d9f0-7647-9e9f-cce1078d5c78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7647-9e9f-cce1078d5c78_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_019dd9a5-d9f0-7647-9e9f-cce1078d5c78" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7647-9e9f-cce1078d5c78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7a04-8180-015f78206228" 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_019dd9a5-d9f0-7647-9e9f-cce1078d5c78" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7a04-8180-015f78206228" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel12And3Member_019dd9a5-d9f0-7a03-a270-83473e4564be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel12And3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019dd9a5-d9f0-7a04-8180-015f78206228" xlink:to="loc_us-gaap_FairValueInputsLevel12And3Member_019dd9a5-d9f0-7a03-a270-83473e4564be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019dd9a5-d9f0-76f1-9e97-57e43c581967" 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_FairValueInputsLevel12And3Member_019dd9a5-d9f0-7a03-a270-83473e4564be" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019dd9a5-d9f0-76f1-9e97-57e43c581967" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019dd9a5-d9f0-776e-9546-f35f5d211982" 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_FairValueInputsLevel12And3Member_019dd9a5-d9f0-7a03-a270-83473e4564be" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019dd9a5-d9f0-776e-9546-f35f5d211982" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019dd9a5-d9f0-77f5-8292-bf773ce31ebd" 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_FairValueInputsLevel12And3Member_019dd9a5-d9f0-7a03-a270-83473e4564be" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019dd9a5-d9f0-77f5-8292-bf773ce31ebd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019dd9a5-d9f0-75e1-b73a-f1e92840624e" 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019dd9a5-d9f0-7cc3-9963-4bdee9db7df6" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019dd9a5-d9f0-75e1-b73a-f1e92840624e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019dd9a5-d9f0-75e1-b73a-f1e92840624e_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_019dd9a5-d9f0-75e1-b73a-f1e92840624e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019dd9a5-d9f0-75e1-b73a-f1e92840624e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019dd9a5-d9f0-7e86-ad36-b964bb927d97" 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_019dd9a5-d9f0-75e1-b73a-f1e92840624e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019dd9a5-d9f0-7e86-ad36-b964bb927d97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019dd9a5-d9f0-71e7-afbd-4bca0038919c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsNonrecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019dd9a5-d9f0-7e86-ad36-b964bb927d97" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019dd9a5-d9f0-71e7-afbd-4bca0038919c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" 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_019dd9a5-d9f0-7282-9a7e-ea1350664f3d" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RestrictedCashAndCashEquivalentsFairValueDisclosure_019dd9a5-d9f0-70d6-b7a7-336c86f8837d" xlink:href="tw-20260630.xsd#tw_RestrictedCashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:to="loc_tw_RestrictedCashAndCashEquivalentsFairValueDisclosure_019dd9a5-d9f0-70d6-b7a7-336c86f8837d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations_019dd9a5-d9f0-75ba-9b61-73d21d3937c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:to="loc_us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations_019dd9a5-d9f0-75ba-9b61-73d21d3937c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsWithClearingOrganizationsAndOthersSecurities_019dd9a5-d9f0-7cdd-b2b1-2a106d51f7c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepositsWithClearingOrganizationsAndOthersSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:to="loc_us-gaap_DepositsWithClearingOrganizationsAndOthersSecurities_019dd9a5-d9f0-7cdd-b2b1-2a106d51f7c6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance_019dd9a5-d9f0-7b05-9685-f82d3a78b902" xlink:href="tw-20260630.xsd#tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:to="loc_tw_AccountReceivableExcludingReceivableFromBrokersAndDealersAndClearingOrganizationsNetOfAllowance_019dd9a5-d9f0-7b05-9685-f82d3a78b902" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesFromClearingOrganizations_019dd9a5-d9f0-77d6-b7cc-f8c4b4a76a04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivablesFromClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:to="loc_us-gaap_ReceivablesFromClearingOrganizations_019dd9a5-d9f0-77d6-b7cc-f8c4b4a76a04" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019dd9a5-d9f0-7f9e-a87d-5a3670632f02" 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_019dd9a5-d9f0-7c8b-8509-54af9d1386d9" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019dd9a5-d9f0-7f9e-a87d-5a3670632f02" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019dd9a5-d9f0-75e0-ba87-4fe48edeaac8" 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_019dd9a5-d9f0-7282-9a7e-ea1350664f3d" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019dd9a5-d9f0-75e0-ba87-4fe48edeaac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_PayablesToBrokerDealersAndClearingOrganizations_019dd9a5-d9f0-70a9-bbcd-ebb75c6258d4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_PayablesToBrokerDealersAndClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019dd9a5-d9f0-75e0-ba87-4fe48edeaac8" xlink:to="loc_srt_PayablesToBrokerDealersAndClearingOrganizations_019dd9a5-d9f0-70a9-bbcd-ebb75c6258d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019dd9a5-d9f0-7054-8527-80dd7a0245b2" 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_019dd9a5-d9f0-75e0-ba87-4fe48edeaac8" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019dd9a5-d9f0-7054-8527-80dd7a0245b2" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CreditRiskDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#CreditRiskDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CreditRiskDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_019dd9a5-d9f0-77da-a92a-3c1ca81739ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_us-gaap_ConcentrationRiskTable_019dd9a5-d9f0-77da-a92a-3c1ca81739ab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7789-8a0b-0f6577446e89" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019dd9a5-d9f0-77da-a92a-3c1ca81739ab" xlink:to="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7789-8a0b-0f6577446e89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7789-8a0b-0f6577446e89_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7789-8a0b-0f6577446e89" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-7789-8a0b-0f6577446e89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-73c7-9c33-3f762c0352c5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CryptoAssetAxis_019dd9a5-d9f0-7789-8a0b-0f6577446e89" xlink:to="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-73c7-9c33-3f762c0352c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DigitalAssetLoanReceivableMember_019dd9a5-d9f0-7cf6-b18d-9a7bcea96ee7" xlink:href="tw-20260630.xsd#tw_DigitalAssetLoanReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CryptoAssetDomain_019dd9a5-d9f0-73c7-9c33-3f762c0352c5" xlink:to="loc_tw_DigitalAssetLoanReceivableMember_019dd9a5-d9f0-7cf6-b18d-9a7bcea96ee7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations_019dd9a5-d9f0-70eb-81c9-310c4e5be176" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations_019dd9a5-d9f0-70eb-81c9-310c4e5be176" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_PayablesToBrokerDealersAndClearingOrganizations_019dd9a5-d9f0-7f4f-9625-eab32ad918a0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_PayablesToBrokerDealersAndClearingOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_srt_PayablesToBrokerDealersAndClearingOrganizations_019dd9a5-d9f0-7f4f-9625-eab32ad918a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_BrokerDealerSelfFundedRemainingDifferenceBetweenFailToDeliverAndFailToReceive_019dd9a5-d9f0-7e95-a509-c05f462ce36d" xlink:href="tw-20260630.xsd#tw_BrokerDealerSelfFundedRemainingDifferenceBetweenFailToDeliverAndFailToReceive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_tw_BrokerDealerSelfFundedRemainingDifferenceBetweenFailToDeliverAndFailToReceive_019dd9a5-d9f0-7e95-a509-c05f462ce36d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d9f0-7c0f-a399-0dbb3a4eb17c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019dd9a5-d9f0-7c0f-a399-0dbb3a4eb17c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_019dd9a5-d9f0-740f-a4d5-9fed2edcd648" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_019dd9a5-d9f0-740f-a4d5-9fed2edcd648" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss_019dd9a5-d9f0-7ac4-a457-86c4a136dcfb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss_019dd9a5-d9f0-7ac4-a457-86c4a136dcfb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded_019dd9a5-d9f0-7a4f-8b7c-a7edec14963a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019dd9a5-d9f0-7245-8253-795f88f48ae3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded_019dd9a5-d9f0-7a4f-8b7c-a7edec14963a" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019dd9a5-d9f0-7fe5-9ff7-debca45fb8cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_LossContingenciesTable_019dd9a5-d9f0-7fe5-9ff7-debca45fb8cf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-79d4-b45c-317b4074590b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019dd9a5-d9f0-7fe5-9ff7-debca45fb8cf" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-79d4-b45c-317b4074590b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-79d4-b45c-317b4074590b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-79d4-b45c-317b4074590b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-79d4-b45c-317b4074590b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7b6d-9140-c8887f79db39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dd9a5-d9f0-79d4-b45c-317b4074590b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7b6d-9140-c8887f79db39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019dd9a5-d9f0-7e08-9f19-15a771200d91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019dd9a5-d9f0-7b6d-9140-c8887f79db39" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019dd9a5-d9f0-7e08-9f19-15a771200d91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019dd9a5-d9f0-7aa7-a066-71a77ff347d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019dd9a5-d9f0-7fe5-9ff7-debca45fb8cf" xlink:to="loc_us-gaap_CreditFacilityAxis_019dd9a5-d9f0-7aa7-a066-71a77ff347d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019dd9a5-d9f0-7aa7-a066-71a77ff347d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019dd9a5-d9f0-7aa7-a066-71a77ff347d6" xlink:to="loc_us-gaap_CreditFacilityDomain_019dd9a5-d9f0-7aa7-a066-71a77ff347d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019dd9a5-d9f0-70e0-974e-c08e6d94c6bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019dd9a5-d9f0-7aa7-a066-71a77ff347d6" xlink:to="loc_us-gaap_CreditFacilityDomain_019dd9a5-d9f0-70e0-974e-c08e6d94c6bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_019dd9a5-d9f0-7834-b51d-ca1be7c40247" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019dd9a5-d9f0-70e0-974e-c08e6d94c6bb" xlink:to="loc_us-gaap_LetterOfCreditMember_019dd9a5-d9f0-7834-b51d-ca1be7c40247" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BridgeLoanMember_019dd9a5-d9f0-75a4-b823-f2e636627a1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BridgeLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019dd9a5-d9f0-70e0-974e-c08e6d94c6bb" xlink:to="loc_us-gaap_BridgeLoanMember_019dd9a5-d9f0-75a4-b823-f2e636627a1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019dd9a5-d9f0-71cf-adb6-2d2c947c81e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019dd9a5-d9f0-7fe5-9ff7-debca45fb8cf" xlink:to="loc_us-gaap_VariableRateAxis_019dd9a5-d9f0-71cf-adb6-2d2c947c81e8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-71cf-adb6-2d2c947c81e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019dd9a5-d9f0-71cf-adb6-2d2c947c81e8" xlink:to="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-71cf-adb6-2d2c947c81e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-7cbb-894e-6222e0415a90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019dd9a5-d9f0-71cf-adb6-2d2c947c81e8" xlink:to="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-7cbb-894e-6222e0415a90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_OneMonthSecuredOvernightFinancingRateMember_019dd9a5-d9f0-73b6-b828-87f8281f60e5" xlink:href="tw-20260630.xsd#tw_OneMonthSecuredOvernightFinancingRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-7cbb-894e-6222e0415a90" xlink:to="loc_tw_OneMonthSecuredOvernightFinancingRateMember_019dd9a5-d9f0-73b6-b828-87f8281f60e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019dd9a5-d9f0-7cef-a238-1a7575664090" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-7cbb-894e-6222e0415a90" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019dd9a5-d9f0-7cef-a238-1a7575664090" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EURIBORMember_019dd9a5-d9f0-7f7d-b04f-1062b334e6d4" xlink:href="tw-20260630.xsd#tw_EURIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-7cbb-894e-6222e0415a90" xlink:to="loc_tw_EURIBORMember_019dd9a5-d9f0-7f7d-b04f-1062b334e6d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019dd9a5-d9f0-7a15-a93b-f31d26f67df5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FederalFundsEffectiveSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019dd9a5-d9f0-7cbb-894e-6222e0415a90" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019dd9a5-d9f0-7a15-a93b-f31d26f67df5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019dd9a5-d9f0-7c69-921f-bfeb5958b75c" 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_LossContingenciesTable_019dd9a5-d9f0-7fe5-9ff7-debca45fb8cf" xlink:to="loc_srt_RangeAxis_019dd9a5-d9f0-7c69-921f-bfeb5958b75c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dd9a5-d9f0-7c69-921f-bfeb5958b75c_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_019dd9a5-d9f0-7c69-921f-bfeb5958b75c" xlink:to="loc_srt_RangeMember_019dd9a5-d9f0-7c69-921f-bfeb5958b75c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dd9a5-d9f0-70a4-821d-a9895586f16c" 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_019dd9a5-d9f0-7c69-921f-bfeb5958b75c" xlink:to="loc_srt_RangeMember_019dd9a5-d9f0-70a4-821d-a9895586f16c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019dd9a5-d9f0-7210-a777-6b6c4947a802" 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_019dd9a5-d9f0-70a4-821d-a9895586f16c" xlink:to="loc_srt_MinimumMember_019dd9a5-d9f0-7210-a777-6b6c4947a802" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019dd9a5-d9f0-701d-9cf4-a39103f25f67" 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_019dd9a5-d9f0-70a4-821d-a9895586f16c" xlink:to="loc_srt_MaximumMember_019dd9a5-d9f0-701d-9cf4-a39103f25f67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019dd9a5-d9f0-7e64-afb3-3ce42ba7c7be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_DebtInstrumentTerm_019dd9a5-d9f0-7e64-afb3-3ce42ba7c7be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019dd9a5-d9f0-7d00-9a94-dce48f8a21c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019dd9a5-d9f0-7d00-9a94-dce48f8a21c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_LineOfCreditFacilityAccordionFeatureIncreaseLimit_019dd9a5-d9f0-74e0-a4bf-a0e501790480" xlink:href="tw-20260630.xsd#tw_LineOfCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_tw_LineOfCreditFacilityAccordionFeatureIncreaseLimit_019dd9a5-d9f0-74e0-a4bf-a0e501790480" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019dd9a5-d9f0-7126-a8bd-802a4aafa3cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019dd9a5-d9f0-7126-a8bd-802a4aafa3cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DebtInstrumentCreditAdjustmentSpread_019dd9a5-d9f1-76a8-b2e2-7d7d0e99c397" xlink:href="tw-20260630.xsd#tw_DebtInstrumentCreditAdjustmentSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_tw_DebtInstrumentCreditAdjustmentSpread_019dd9a5-d9f1-76a8-b2e2-7d7d0e99c397" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DebtInstrumentAdjustmentInAdditionToCreditAdjustmentSpread_019dd9a5-d9f1-7848-baee-7fdb344a8b80" xlink:href="tw-20260630.xsd#tw_DebtInstrumentAdjustmentInAdditionToCreditAdjustmentSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_tw_DebtInstrumentAdjustmentInAdditionToCreditAdjustmentSpread_019dd9a5-d9f1-7848-baee-7fdb344a8b80" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DebtInstrumentFloorRate_019dd9a5-d9f1-7776-87e7-f16fa58ba46e" xlink:href="tw-20260630.xsd#tw_DebtInstrumentFloorRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_tw_DebtInstrumentFloorRate_019dd9a5-d9f1-7776-87e7-f16fa58ba46e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_019dd9a5-d9f1-7912-a6ac-22148962c0ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_019dd9a5-d9f1-7912-a6ac-22148962c0ef" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019dd9a5-d9f1-7cd1-b36a-46a75a255d2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019dd9a5-d9f1-7cd1-b36a-46a75a255d2e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019dd9a5-d9f1-75b5-811d-cc5d75ffbb6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019dd9a5-d9f1-75b5-811d-cc5d75ffbb6d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_019dd9a5-d9f1-77f8-93ca-ec1140ba47ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019dd9a5-d9f0-7a3e-8de2-6edbb24fc774" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_019dd9a5-d9f1-77f8-93ca-ec1140ba47ed" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/EarningsPerShareScheduleofBasicandDilutedEarningsPerShareDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#EarningsPerShareScheduleofBasicandDilutedEarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/EarningsPerShareScheduleofBasicandDilutedEarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasicLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_019dd9a5-d9f1-778d-abf7-8d53d69ab5ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_019dd9a5-d9f1-778d-abf7-8d53d69ab5ea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019dd9a5-d9f1-75a4-9937-f3794d5d1fee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_019dd9a5-d9f1-778d-abf7-8d53d69ab5ea" xlink:to="loc_us-gaap_AwardTypeAxis_019dd9a5-d9f1-75a4-9937-f3794d5d1fee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-75a4-9937-f3794d5d1fee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019dd9a5-d9f1-75a4-9937-f3794d5d1fee" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-75a4-9937-f3794d5d1fee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-7be9-932d-23eb4a2312e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019dd9a5-d9f1-75a4-9937-f3794d5d1fee" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-7be9-932d-23eb4a2312e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember_019dd9a5-d9f1-78e7-88a6-1b98e898cf91" xlink:href="tw-20260630.xsd#tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-7be9-932d-23eb4a2312e2" xlink:to="loc_tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember_019dd9a5-d9f1-78e7-88a6-1b98e898cf91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019dd9a5-d9f1-7b74-82e6-2a31436eded0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-7be9-932d-23eb4a2312e2" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019dd9a5-d9f1-7b74-82e6-2a31436eded0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RestrictedStockUnitsAndRestrictedStockMember_019dd9a5-d9f1-7b2b-a744-6a5aec700760" xlink:href="tw-20260630.xsd#tw_RestrictedStockUnitsAndRestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-7be9-932d-23eb4a2312e2" xlink:to="loc_tw_RestrictedStockUnitsAndRestrictedStockMember_019dd9a5-d9f1-7b2b-a744-6a5aec700760" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d9f1-71b6-babb-ba1e2da6e7cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019dd9a5-d9f1-7be9-932d-23eb4a2312e2" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d9f1-71b6-babb-ba1e2da6e7cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAbstract_019dd9a5-d9f1-74e0-a452-90a8b005c6b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:to="loc_us-gaap_NetIncomeLossAbstract_019dd9a5-d9f1-74e0-a452-90a8b005c6b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019dd9a5-d9f1-72e6-9966-072774196404" 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_NetIncomeLossAbstract_019dd9a5-d9f1-74e0-a452-90a8b005c6b3" xlink:to="loc_us-gaap_NetIncomeLoss_019dd9a5-d9f1-72e6-9966-072774196404" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic_019dd9a5-d9f1-7a10-80dc-fda78ca15317" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAbstract_019dd9a5-d9f1-74e0-a452-90a8b005c6b3" xlink:to="loc_us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic_019dd9a5-d9f1-7a10-80dc-fda78ca15317" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019dd9a5-d9f1-786a-b913-fefb9d0e0c33" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAbstract_019dd9a5-d9f1-74e0-a452-90a8b005c6b3" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019dd9a5-d9f1-786a-b913-fefb9d0e0c33" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_019dd9a5-d9f1-7ffb-9ebe-40fc3192089d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAbstract_019dd9a5-d9f1-74e0-a452-90a8b005c6b3" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_019dd9a5-d9f1-7ffb-9ebe-40fc3192089d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_019dd9a5-d9f1-7831-9275-6c44d03144fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_019dd9a5-d9f1-7831-9275-6c44d03144fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019dd9a5-d9f1-7345-89de-3455ee0d3577" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_019dd9a5-d9f1-7831-9275-6c44d03144fc" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019dd9a5-d9f1-7345-89de-3455ee0d3577" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019dd9a5-d9f1-7eba-a18c-58edc1e3fd09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_019dd9a5-d9f1-7831-9275-6c44d03144fc" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019dd9a5-d9f1-7eba-a18c-58edc1e3fd09" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019dd9a5-d9f1-7ca7-a16a-eaaaa3f91545" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_019dd9a5-d9f1-7831-9275-6c44d03144fc" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019dd9a5-d9f1-7ca7-a16a-eaaaa3f91545" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019dd9a5-d9f1-7c8d-a9a2-317b958a0b9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:to="loc_us-gaap_EarningsPerShareBasic_019dd9a5-d9f1-7c8d-a9a2-317b958a0b9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019dd9a5-d9f1-755e-a772-27a7deb42158" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019dd9a5-d9f1-755e-a772-27a7deb42158" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossShares_019dd9a5-d9f1-7df8-95e5-b955b4111d75" xlink:href="tw-20260630.xsd#tw_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_019dd9a5-d9f1-7b03-a6c5-7b0588f005ca" xlink:to="loc_tw_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossShares_019dd9a5-d9f1-7df8-95e5-b955b4111d75" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/EarningsPerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#EarningsPerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/EarningsPerShareScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019dd9a5-d9f1-7056-a652-da74bd278417" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019dd9a5-d9f1-7037-81c1-ced53de31909" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019dd9a5-d9f1-7056-a652-da74bd278417" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019dd9a5-d9f1-7037-81c1-ced53de31909" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019dd9a5-d9f1-753a-bf14-45625cbb620f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019dd9a5-d9f1-7037-81c1-ced53de31909" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019dd9a5-d9f1-753a-bf14-45625cbb620f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-753a-bf14-45625cbb620f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019dd9a5-d9f1-753a-bf14-45625cbb620f" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-753a-bf14-45625cbb620f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019dd9a5-d9f1-753a-bf14-45625cbb620f" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember_019dd9a5-d9f1-7c6d-83bb-b8361be0bafe" xlink:href="tw-20260630.xsd#tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:to="loc_tw_EquitySettledPerformanceBasedRestrictedStockUnitsMember_019dd9a5-d9f1-7c6d-83bb-b8361be0bafe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019dd9a5-d9f1-73b6-b700-51643692e2a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019dd9a5-d9f1-73b6-b700-51643692e2a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RestrictedStockUnitsAndRestrictedStockMember_019dd9a5-d9f1-7510-9b12-d21f117c3eb2" xlink:href="tw-20260630.xsd#tw_RestrictedStockUnitsAndRestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:to="loc_tw_RestrictedStockUnitsAndRestrictedStockMember_019dd9a5-d9f1-7510-9b12-d21f117c3eb2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d9f1-7921-bdad-c5ef03a8b84c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_019dd9a5-d9f1-7921-bdad-c5ef03a8b84c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_LimitedLiabilityCompanyUnitsMember_019dd9a5-d9f1-79ae-a271-ef862fde7f97" xlink:href="tw-20260630.xsd#tw_LimitedLiabilityCompanyUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019dd9a5-d9f1-732d-bdfa-492391893c54" xlink:to="loc_tw_LimitedLiabilityCompanyUnitsMember_019dd9a5-d9f1-79ae-a271-ef862fde7f97" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019dd9a5-d9f1-7fa5-aa54-09623dacb8cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019dd9a5-d9f1-7056-a652-da74bd278417" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019dd9a5-d9f1-7fa5-aa54-09623dacb8cc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/RegulatoryCapitalRequirementsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#RegulatoryCapitalRequirementsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/RegulatoryCapitalRequirementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019dd9a5-d9f1-7bcd-8844-a5db7abf2789" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019dd9a5-d9f1-73db-9f3e-869c1ee1ff7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019dd9a5-d9f1-7bcd-8844-a5db7abf2789" xlink:to="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019dd9a5-d9f1-73db-9f3e-869c1ee1ff7e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019dd9a5-d9f1-7bd3-83d9-8ac91d784a34" 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_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019dd9a5-d9f1-73db-9f3e-869c1ee1ff7e" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019dd9a5-d9f1-7bd3-83d9-8ac91d784a34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-7bd3-83d9-8ac91d784a34_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_019dd9a5-d9f1-7bd3-83d9-8ac91d784a34" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-7bd3-83d9-8ac91d784a34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" 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_019dd9a5-d9f1-7bd3-83d9-8ac91d784a34" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebLlcMember_019dd9a5-d9f1-77e0-9521-ef80494c1f64" xlink:href="tw-20260630.xsd#tw_TradewebLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebLlcMember_019dd9a5-d9f1-77e0-9521-ef80494c1f64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DealerwebMember_019dd9a5-d9f1-739c-b3aa-d6786142e857" xlink:href="tw-20260630.xsd#tw_DealerwebMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_DealerwebMember_019dd9a5-d9f1-739c-b3aa-d6786142e857" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebDirectLlcMember_019dd9a5-d9f1-7295-8aa5-7636d1c49ddc" xlink:href="tw-20260630.xsd#tw_TradewebDirectLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebDirectLlcMember_019dd9a5-d9f1-7295-8aa5-7636d1c49ddc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebEuropeLimitedMember_019dd9a5-d9f1-7e7d-b44a-eb7384e5691a" xlink:href="tw-20260630.xsd#tw_TradewebEuropeLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebEuropeLimitedMember_019dd9a5-d9f1-7e7d-b44a-eb7384e5691a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebJapanKkMember_019dd9a5-d9f1-7cf6-9729-58b7716d3a4d" xlink:href="tw-20260630.xsd#tw_TradewebJapanKkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebJapanKkMember_019dd9a5-d9f1-7cf6-9729-58b7716d3a4d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebEuBvMember_019dd9a5-d9f1-74eb-a2b2-c5237f8b4902" xlink:href="tw-20260630.xsd#tw_TradewebEuBvMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebEuBvMember_019dd9a5-d9f1-74eb-a2b2-c5237f8b4902" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebExecutionServicesLimitedMember_019dd9a5-d9f1-7d9e-a1af-b80be77470ac" xlink:href="tw-20260630.xsd#tw_TradewebExecutionServicesLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebExecutionServicesLimitedMember_019dd9a5-d9f1-7d9e-a1af-b80be77470ac" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebExecutionServicesBVMember_019dd9a5-d9f1-7576-8422-b9031128668f" xlink:href="tw-20260630.xsd#tw_TradewebExecutionServicesBVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebExecutionServicesBVMember_019dd9a5-d9f1-7576-8422-b9031128668f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_YieldbrokerMember_019dd9a5-d9f1-7aa5-b064-c677acafea65" xlink:href="tw-20260630.xsd#tw_YieldbrokerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_YieldbrokerMember_019dd9a5-d9f1-7aa5-b064-c677acafea65" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebLimitedMember_019dd9a5-d9f1-73d4-bd9d-dfab3fd50bda" xlink:href="tw-20260630.xsd#tw_TradewebLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebLimitedMember_019dd9a5-d9f1-73d4-bd9d-dfab3fd50bda" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_InstitutionalCashDistributorsMember_019dd9a5-d9f1-7747-9991-4a8fc7302475" xlink:href="tw-20260630.xsd#tw_InstitutionalCashDistributorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_InstitutionalCashDistributorsMember_019dd9a5-d9f1-7747-9991-4a8fc7302475" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_InstitutionalCashDistributorsLimitedMember_019dd9a5-d9f1-7d7e-958f-11d03a703aca" xlink:href="tw-20260630.xsd#tw_InstitutionalCashDistributorsLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_InstitutionalCashDistributorsLimitedMember_019dd9a5-d9f1-7d7e-958f-11d03a703aca" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebSaudiArabiaMember_019dd9a5-d9f1-71a3-895d-1bbe899d31f0" xlink:href="tw-20260630.xsd#tw_TradewebSaudiArabiaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebSaudiArabiaMember_019dd9a5-d9f1-71a3-895d-1bbe899d31f0" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TradewebAsiaPte.Ltd.Member_019dd9a5-d9f1-7492-9465-d628696a0132" xlink:href="tw-20260630.xsd#tw_TradewebAsiaPte.Ltd.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TradewebAsiaPte.Ltd.Member_019dd9a5-d9f1-7492-9465-d628696a0132" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TwSefLlcMember_019dd9a5-d9f1-773e-bb66-2b281973a04c" xlink:href="tw-20260630.xsd#tw_TwSefLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_TwSefLlcMember_019dd9a5-d9f1-773e-bb66-2b281973a04c" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DwSefLlcMember_019dd9a5-d9f1-7914-9875-f1ed78e2f054" xlink:href="tw-20260630.xsd#tw_DwSefLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019dd9a5-d9f1-792f-b26f-c101b09d8691" xlink:to="loc_tw_DwSefLlcMember_019dd9a5-d9f1-7914-9875-f1ed78e2f054" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RegulatoryCapital_019dd9a5-d9f1-7dfe-b8fc-5ac96aabe5c1" xlink:href="tw-20260630.xsd#tw_RegulatoryCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019dd9a5-d9f1-7bcd-8844-a5db7abf2789" xlink:to="loc_tw_RegulatoryCapital_019dd9a5-d9f1-7dfe-b8fc-5ac96aabe5c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RegulatoryCapitalRequirement_019dd9a5-d9f1-72a4-8c62-8fcf20154f79" xlink:href="tw-20260630.xsd#tw_RegulatoryCapitalRequirement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_tw_RegulatoryCapital_019dd9a5-d9f1-7dfe-b8fc-5ac96aabe5c1" xlink:to="loc_tw_RegulatoryCapitalRequirement_019dd9a5-d9f1-72a4-8c62-8fcf20154f79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ExcessRegulatoryCapital_019dd9a5-d9f1-7d25-9834-7c2c2711f824" xlink:href="tw-20260630.xsd#tw_ExcessRegulatoryCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_tw_RegulatoryCapital_019dd9a5-d9f1-7dfe-b8fc-5ac96aabe5c1" xlink:to="loc_tw_ExcessRegulatoryCapital_019dd9a5-d9f1-7d25-9834-7c2c2711f824" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NetCapitalUnderCommodityExchangeActComputation_019dd9a5-d9f1-7fcc-a9f1-f52723ae36cd" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NetCapitalUnderCommodityExchangeActComputation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019dd9a5-d9f1-7bcd-8844-a5db7abf2789" xlink:to="loc_srt_NetCapitalUnderCommodityExchangeActComputation_019dd9a5-d9f1-7fcc-a9f1-f52723ae36cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RequiredNetCapitalUnderCommodityExchangeAct1_019dd9a5-d9f1-71e5-a4fb-1fe75d8a0a8c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RequiredNetCapitalUnderCommodityExchangeAct1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NetCapitalUnderCommodityExchangeActComputation_019dd9a5-d9f1-7fcc-a9f1-f52723ae36cd" xlink:to="loc_srt_RequiredNetCapitalUnderCommodityExchangeAct1_019dd9a5-d9f1-71e5-a4fb-1fe75d8a0a8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NetCapitalExcessShortageUnderCommodityExchangeAct_019dd9a5-d9f1-7352-85c9-030ce408b461" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NetCapitalExcessShortageUnderCommodityExchangeAct"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NetCapitalUnderCommodityExchangeActComputation_019dd9a5-d9f1-7fcc-a9f1-f52723ae36cd" xlink:to="loc_srt_NetCapitalExcessShortageUnderCommodityExchangeAct_019dd9a5-d9f1-7352-85c9-030ce408b461" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_LiquidFinancialAssets_019dd9a5-d9f1-751b-b218-7e7183790542" xlink:href="tw-20260630.xsd#tw_LiquidFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019dd9a5-d9f1-7bcd-8844-a5db7abf2789" xlink:to="loc_tw_LiquidFinancialAssets_019dd9a5-d9f1-751b-b218-7e7183790542" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RequiredLiquidFinancialAssets_019dd9a5-d9f1-731f-bbf5-8c18951a9713" xlink:href="tw-20260630.xsd#tw_RequiredLiquidFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_tw_LiquidFinancialAssets_019dd9a5-d9f1-751b-b218-7e7183790542" xlink:to="loc_tw_RequiredLiquidFinancialAssets_019dd9a5-d9f1-731f-bbf5-8c18951a9713" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ExcessLiquidFinancialAssets_019dd9a5-d9f1-70be-b1fa-9ba5148e6e8f" xlink:href="tw-20260630.xsd#tw_ExcessLiquidFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_tw_LiquidFinancialAssets_019dd9a5-d9f1-751b-b218-7e7183790542" xlink:to="loc_tw_ExcessLiquidFinancialAssets_019dd9a5-d9f1-70be-b1fa-9ba5148e6e8f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/BusinessSegmentandGeographicInformationScheduleofInformationRegardingRevenuebyClientSectorDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#BusinessSegmentandGeographicInformationScheduleofInformationRegardingRevenuebyClientSectorDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/BusinessSegmentandGeographicInformationScheduleofInformationRegardingRevenuebyClientSectorDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" 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_019dd9a5-d9f1-76e7-93f3-eada9cbc193c" 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_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019dd9a5-d9f1-76e7-93f3-eada9cbc193c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019dd9a5-d9f1-7942-8570-384201bc4263" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019dd9a5-d9f1-76e7-93f3-eada9cbc193c" xlink:to="loc_srt_MajorCustomersAxis_019dd9a5-d9f1-7942-8570-384201bc4263" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7942-8570-384201bc4263_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019dd9a5-d9f1-7942-8570-384201bc4263" xlink:to="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7942-8570-384201bc4263_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019dd9a5-d9f1-7942-8570-384201bc4263" xlink:to="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_InstitutionalClientSectorMember_019dd9a5-d9f1-73d7-9301-daed1b6149cc" xlink:href="tw-20260630.xsd#tw_InstitutionalClientSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:to="loc_tw_InstitutionalClientSectorMember_019dd9a5-d9f1-73d7-9301-daed1b6149cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_WholesaleClientSectorMember_019dd9a5-d9f1-7fdb-9b23-8c968fb22949" xlink:href="tw-20260630.xsd#tw_WholesaleClientSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:to="loc_tw_WholesaleClientSectorMember_019dd9a5-d9f1-7fdb-9b23-8c968fb22949" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_RetailClientSectorMember_019dd9a5-d9f1-788d-8310-ec265479e726" xlink:href="tw-20260630.xsd#tw_RetailClientSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:to="loc_tw_RetailClientSectorMember_019dd9a5-d9f1-788d-8310-ec265479e726" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_CorporateClientSectorMember_019dd9a5-d9f1-7581-bb73-3db44872557b" xlink:href="tw-20260630.xsd#tw_CorporateClientSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:to="loc_tw_CorporateClientSectorMember_019dd9a5-d9f1-7581-bb73-3db44872557b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_MarketDataClientSectorMember_019dd9a5-d9f1-7a2e-9ea2-8d327daca7ee" xlink:href="tw-20260630.xsd#tw_MarketDataClientSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019dd9a5-d9f1-7522-b07b-54dc3d211a94" xlink:to="loc_tw_MarketDataClientSectorMember_019dd9a5-d9f1-7a2e-9ea2-8d327daca7ee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019dd9a5-d9f1-7c76-8ca9-92659aab35f0" 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_019dd9a5-d9f1-76e7-93f3-eada9cbc193c" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019dd9a5-d9f1-7c76-8ca9-92659aab35f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019dd9a5-d9f1-7c76-8ca9-92659aab35f0_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_019dd9a5-d9f1-7c76-8ca9-92659aab35f0" xlink:to="loc_us-gaap_SegmentDomain_019dd9a5-d9f1-7c76-8ca9-92659aab35f0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019dd9a5-d9f1-78ff-b4e9-17a03d0f8191" 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_019dd9a5-d9f1-7c76-8ca9-92659aab35f0" xlink:to="loc_us-gaap_SegmentDomain_019dd9a5-d9f1-78ff-b4e9-17a03d0f8191" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_ReportableSegmentMember_019dd9a5-d9f1-741b-977c-ab000f0cc7ac" xlink:href="tw-20260630.xsd#tw_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019dd9a5-d9f1-78ff-b4e9-17a03d0f8191" xlink:to="loc_tw_ReportableSegmentMember_019dd9a5-d9f1-741b-977c-ab000f0cc7ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f1-78ad-941c-7dafab997931" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f1-78ad-941c-7dafab997931" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019dd9a5-d9f1-7cec-900c-9bb30db0785f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019dd9a5-d9f1-7cec-900c-9bb30db0785f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_019dd9a5-d9f1-7aeb-975e-3abde7b9d229" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommunicationsAndInformationTechnology"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_019dd9a5-d9f1-7aeb-975e-3abde7b9d229" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019dd9a5-d9f1-7f60-94a7-55ebcdc90dbc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019dd9a5-d9f1-7f60-94a7-55ebcdc90dbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019dd9a5-d9f1-7cac-a28c-e87b2cd08d2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_ProfessionalFees_019dd9a5-d9f1-7cac-a28c-e87b2cd08d2d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_019dd9a5-d9f1-72be-9dd4-a6a0c1c0fb87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OccupancyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_OccupancyNet_019dd9a5-d9f1-72be-9dd4-a6a0c1c0fb87" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_019dd9a5-d9f1-738b-95e8-ff585aa9855b" 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_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_019dd9a5-d9f1-738b-95e8-ff585aa9855b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019dd9a5-d9f1-77a7-b93f-97f08f7ecbf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019dd9a5-d9f1-748f-89f6-9f5c7e0ebe76" xlink:to="loc_us-gaap_ProfitLoss_019dd9a5-d9f1-77a7-b93f-97f08f7ecbf7" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/BusinessSegmentandGeographicInformationScheduleofRevenueandLongLivedAssetsbyGeographicLocationDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#BusinessSegmentandGeographicInformationScheduleofRevenueandLongLivedAssetsbyGeographicLocationDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/BusinessSegmentandGeographicInformationScheduleofRevenueandLongLivedAssetsbyGeographicLocationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019dd9a5-d9f1-7dd1-95ab-a71f9e62abb8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019dd9a5-d9f1-7b48-acb5-a1cc1c61044f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019dd9a5-d9f1-7dd1-95ab-a71f9e62abb8" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019dd9a5-d9f1-7b48-acb5-a1cc1c61044f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019dd9a5-d9f1-76fa-b4a0-8ed6054424cc" 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_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019dd9a5-d9f1-7b48-acb5-a1cc1c61044f" xlink:to="loc_srt_StatementGeographicalAxis_019dd9a5-d9f1-76fa-b4a0-8ed6054424cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019dd9a5-d9f1-76fa-b4a0-8ed6054424cc_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_019dd9a5-d9f1-76fa-b4a0-8ed6054424cc" xlink:to="loc_srt_SegmentGeographicalDomain_019dd9a5-d9f1-76fa-b4a0-8ed6054424cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019dd9a5-d9f1-7658-a8b2-f21760a98e48" 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_019dd9a5-d9f1-76fa-b4a0-8ed6054424cc" xlink:to="loc_srt_SegmentGeographicalDomain_019dd9a5-d9f1-7658-a8b2-f21760a98e48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019dd9a5-d9f1-7d5b-bc8b-1a1affd97df5" 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_019dd9a5-d9f1-7658-a8b2-f21760a98e48" xlink:to="loc_country_US_019dd9a5-d9f1-7d5b-bc8b-1a1affd97df5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019dd9a5-d9f1-7e26-9930-c2fb44252768" 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_019dd9a5-d9f1-7658-a8b2-f21760a98e48" xlink:to="loc_us-gaap_NonUsMember_019dd9a5-d9f1-7e26-9930-c2fb44252768" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f1-7378-b785-6622f08c4bd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019dd9a5-d9f1-7dd1-95ab-a71f9e62abb8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019dd9a5-d9f1-7378-b785-6622f08c4bd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncurrentAssets_019dd9a5-d9f1-7b38-850f-ddece3e7792e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019dd9a5-d9f1-7dd1-95ab-a71f9e62abb8" xlink:to="loc_us-gaap_NoncurrentAssets_019dd9a5-d9f1-7b38-850f-ddece3e7792e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.tradeweb.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="tw-20260630.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.tradeweb.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019dd9a5-d9f1-7818-9c92-cae1c379efe9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019dd9a5-d9f1-7436-bcf7-7179bcec64e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019dd9a5-d9f1-7818-9c92-cae1c379efe9" xlink:to="loc_us-gaap_SubsequentEventTable_019dd9a5-d9f1-7436-bcf7-7179bcec64e6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019dd9a5-d9f1-7805-a474-2eeaf15eb628" 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_SubsequentEventTable_019dd9a5-d9f1-7436-bcf7-7179bcec64e6" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019dd9a5-d9f1-7805-a474-2eeaf15eb628" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dd9a5-d9f1-7805-a474-2eeaf15eb628_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_019dd9a5-d9f1-7805-a474-2eeaf15eb628" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dd9a5-d9f1-7805-a474-2eeaf15eb628_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dd9a5-d9f1-7066-9120-8e4fbc8f149c" 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_019dd9a5-d9f1-7805-a474-2eeaf15eb628" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dd9a5-d9f1-7066-9120-8e4fbc8f149c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019dd9a5-d9f1-7c59-8709-6d43ddffa748" 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_019dd9a5-d9f1-7066-9120-8e4fbc8f149c" xlink:to="loc_us-gaap_SubsequentEventMember_019dd9a5-d9f1-7c59-8709-6d43ddffa748" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d9f1-74e8-8c4b-e1432c8de0d7" 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_us-gaap_SubsequentEventTable_019dd9a5-d9f1-7436-bcf7-7179bcec64e6" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd9a5-d9f1-74e8-8c4b-e1432c8de0d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d9f1-74e8-8c4b-e1432c8de0d7_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_019dd9a5-d9f1-74e8-8c4b-e1432c8de0d7" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d9f1-74e8-8c4b-e1432c8de0d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd9a5-d9f1-7e09-808e-d7cc6bb55224" 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_019dd9a5-d9f1-74e8-8c4b-e1432c8de0d7" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd9a5-d9f1-7e09-808e-d7cc6bb55224" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019dd9a5-d9f1-7d61-a7bd-0bb96a705834" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d9f1-7e09-808e-d7cc6bb55224" xlink:to="loc_us-gaap_CommonClassAMember_019dd9a5-d9f1-7d61-a7bd-0bb96a705834" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019dd9a5-d9f1-7a10-8e8e-3afd67c3e733" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd9a5-d9f1-7e09-808e-d7cc6bb55224" xlink:to="loc_us-gaap_CommonClassBMember_019dd9a5-d9f1-7a10-8e8e-3afd67c3e733" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019dd9a5-d9f1-7da0-af06-443fc881a8c0" 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_SubsequentEventTable_019dd9a5-d9f1-7436-bcf7-7179bcec64e6" xlink:to="loc_dei_LegalEntityAxis_019dd9a5-d9f1-7da0-af06-443fc881a8c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019dd9a5-d9f1-7da0-af06-443fc881a8c0_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_019dd9a5-d9f1-7da0-af06-443fc881a8c0" xlink:to="loc_dei_EntityDomain_019dd9a5-d9f1-7da0-af06-443fc881a8c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019dd9a5-d9f1-7c21-86c9-b49dbccef3c7" 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_019dd9a5-d9f1-7da0-af06-443fc881a8c0" xlink:to="loc_dei_EntityDomain_019dd9a5-d9f1-7c21-86c9-b49dbccef3c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TWMLLCMember_019dd9a5-d9f1-7e8f-a25e-28afc940fa1b" xlink:href="tw-20260630.xsd#tw_TWMLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019dd9a5-d9f1-7c21-86c9-b49dbccef3c7" xlink:to="loc_tw_TWMLLCMember_019dd9a5-d9f1-7e8f-a25e-28afc940fa1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019dd9a5-d9f1-75b4-a2bf-9103b71ac982" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019dd9a5-d9f1-7818-9c92-cae1c379efe9" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019dd9a5-d9f1-75b4-a2bf-9103b71ac982" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_019dd9a5-d9f1-7879-85ef-6731705aae58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019dd9a5-d9f1-7818-9c92-cae1c379efe9" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_019dd9a5-d9f1-7879-85ef-6731705aae58" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_TroyDixonMember_019ed9e9-d804-7d2e-916e-02715c86c75e" xlink:href="tw-20260630.xsd#tw_TroyDixonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_tw_TroyDixonMember_019ed9e9-d804-7d2e-916e-02715c86c75e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanMember_019dd9a5-d708-79f5-b6f5-ba4657030e96" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_tw_DouglasFriedmanMember_019dd9a5-d708-79f5-b6f5-ba4657030e96" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#TradingArrangmentsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllTradingArrangementsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllTradingArrangementsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockMember_019ed9f7-ec7e-76b0-abc4-81f69b49cd56" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementClassACommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockMember_019ed9f7-ec7e-76b0-abc4-81f69b49cd56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementPerformanceBasedRestrictedStockUnitsVestingPeriodOfJanuary12024January12027Member_019f643a-ddd5-7284-a7da-ffb423e7f68e" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementPerformanceBasedRestrictedStockUnitsVestingPeriodOfJanuary12024January12027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementPerformanceBasedRestrictedStockUnitsVestingPeriodOfJanuary12024January12027Member_019f643a-ddd5-7284-a7da-ffb423e7f68e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockUponVestedOnMarch152027Member_019f643c-d7b1-76d9-b568-c24b00f6a116" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementClassACommonStockUponVestedOnMarch152027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockUponVestedOnMarch152027Member_019f643c-d7b1-76d9-b568-c24b00f6a116" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch152024March152027Member_019f643e-bc5f-7bae-8110-7d597a4c9b57" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch152024March152027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch152024March152027Member_019f643e-bc5f-7bae-8110-7d597a4c9b57" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockVestedOnMarch152027Member_019f6441-0894-7b2f-9cdf-81a9f80703dc" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementClassACommonStockVestedOnMarch152027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockVestedOnMarch152027Member_019f6441-0894-7b2f-9cdf-81a9f80703dc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch152026March152027Member_019f647f-8540-75aa-a48d-51cd02ae0854" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch152026March152027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch152026March152027Member_019f647f-8540-75aa-a48d-51cd02ae0854" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockUponVestedOnMarch172027Member_019f647d-fcda-7fea-b3b8-3b8cf25d061e" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementClassACommonStockUponVestedOnMarch172027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementClassACommonStockUponVestedOnMarch172027Member_019f647d-fcda-7fea-b3b8-3b8cf25d061e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch172025March172027Member_019f6480-934e-7818-9ff4-093dc607c26c" xlink:href="tw-20260630.xsd#tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch172025March172027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_tw_DouglasFriedmanTradingArrangementRestrictedStockUnitsVestingPeriodOfMarch172025March172027Member_019f6480-934e-7818-9ff4-093dc607c26c" xlink:type="arc" order="8"/>
  </link:definitionLink>
</link:linkbase>
