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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019d88ce-392a-76db-adf8-f2fdd2493eb8,g:0162fcc4-c597-450f-9160-fe01262013aa-->
<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.mountlogancapital.ca/role/Cover" xlink:type="simple" xlink:href="yukon-20260409.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.mountlogancapital.ca/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressesTable_019d88ce-392a-7c76-a689-ef898b95f18a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityAddressesTable_019d88ce-392a-7c76-a689-ef898b95f18a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019d88ce-392a-7e80-a223-2d22c5c2642f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntityAddressesTable_019d88ce-392a-7c76-a689-ef898b95f18a" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019d88ce-392a-7e80-a223-2d22c5c2642f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019d88ce-392a-7e80-a223-2d22c5c2642f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019d88ce-392a-7e80-a223-2d22c5c2642f" xlink:to="loc_us-gaap_ClassOfStockDomain_019d88ce-392a-7e80-a223-2d22c5c2642f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019d88ce-392a-7c1e-96a6-cb9f7ecf7d74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019d88ce-392a-7e80-a223-2d22c5c2642f" xlink:to="loc_us-gaap_ClassOfStockDomain_019d88ce-392a-7c1e-96a6-cb9f7ecf7d74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019d88ce-392a-7315-be8d-eb5bf708f049" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d88ce-392a-7c1e-96a6-cb9f7ecf7d74" xlink:to="loc_us-gaap_CommonStockMember_019d88ce-392a-7315-be8d-eb5bf708f049" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_yukon_SeniorNoteDue2031Member_019d88ce-392a-7a3b-a1a0-ffe0f9d1c1da" xlink:href="yukon-20260409.xsd#yukon_SeniorNoteDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d88ce-392a-7c1e-96a6-cb9f7ecf7d74" xlink:to="loc_yukon_SeniorNoteDue2031Member_019d88ce-392a-7a3b-a1a0-ffe0f9d1c1da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019d88ce-392a-776f-9a31-7908424312b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntityAddressesTable_019d88ce-392a-7c76-a689-ef898b95f18a" xlink:to="loc_us-gaap_DebtInstrumentAxis_019d88ce-392a-776f-9a31-7908424312b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019d88ce-392a-776f-9a31-7908424312b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019d88ce-392a-776f-9a31-7908424312b4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019d88ce-392a-776f-9a31-7908424312b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019d88ce-392a-7b77-84a1-2d5e47f43bc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019d88ce-392a-776f-9a31-7908424312b4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019d88ce-392a-7b77-84a1-2d5e47f43bc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019d88ce-392a-7813-9f7f-abbed0807176" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_DocumentType_019d88ce-392a-7813-9f7f-abbed0807176" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019d88ce-392a-7f16-9ab4-306612a125cf" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_DocumentPeriodEndDate_019d88ce-392a-7f16-9ab4-306612a125cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019d88ce-392a-7105-87b2-2d941bfce7a0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityRegistrantName_019d88ce-392a-7105-87b2-2d941bfce7a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019d88ce-392a-7c48-b67f-ee7f09f32d75" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019d88ce-392a-7c48-b67f-ee7f09f32d75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019d88ce-392a-7e91-b60c-10dad0ca6d3f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityFileNumber_019d88ce-392a-7e91-b60c-10dad0ca6d3f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019d88ce-392a-78b8-a4ce-b762fa80391b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityTaxIdentificationNumber_019d88ce-392a-78b8-a4ce-b762fa80391b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019d88ce-392a-782d-a002-276365acee59" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityAddressAddressLine1_019d88ce-392a-782d-a002-276365acee59" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019d88ce-392a-78e7-9200-7bbb656d718b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityAddressAddressLine2_019d88ce-392a-78e7-9200-7bbb656d718b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019d88ce-392a-7f77-8ca5-230ee69ba1b3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityAddressCityOrTown_019d88ce-392a-7f77-8ca5-230ee69ba1b3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019d88ce-392a-778f-8506-278f703107e2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityAddressStateOrProvince_019d88ce-392a-778f-8506-278f703107e2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019d88ce-392a-7329-a8a2-38f6adc6a559" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityAddressPostalZipCode_019d88ce-392a-7329-a8a2-38f6adc6a559" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019d88ce-392a-7d70-ae9a-7edcaa22ebf2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_CityAreaCode_019d88ce-392a-7d70-ae9a-7edcaa22ebf2" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019d88ce-392a-7a80-bc0b-f1102dfd474d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_LocalPhoneNumber_019d88ce-392a-7a80-bc0b-f1102dfd474d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019d88ce-392a-770b-bb23-4b6c265124de" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_WrittenCommunications_019d88ce-392a-770b-bb23-4b6c265124de" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019d88ce-392a-75f0-aedb-39cef7cbc007" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_SolicitingMaterial_019d88ce-392a-75f0-aedb-39cef7cbc007" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019d88ce-392a-74cb-89cc-b0eadd9b1a8f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_PreCommencementTenderOffer_019d88ce-392a-74cb-89cc-b0eadd9b1a8f" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019d88ce-392a-7520-b92e-2af9d411b009" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019d88ce-392a-7520-b92e-2af9d411b009" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019d88ce-392a-7f1b-81ae-13832aa22442" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_Security12bTitle_019d88ce-392a-7f1b-81ae-13832aa22442" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019d88ce-392a-7927-a29f-44dbaf242b2a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_TradingSymbol_019d88ce-392a-7927-a29f-44dbaf242b2a" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019d88ce-392a-7864-a014-76291a43ba05" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_SecurityExchangeName_019d88ce-392a-7864-a014-76291a43ba05" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019d88ce-392a-7c50-8566-bae0969f0c00" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityEmergingGrowthCompany_019d88ce-392a-7c50-8566-bae0969f0c00" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_019d88ce-392a-76d0-bd98-5be920ff6152" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityExTransitionPeriod_019d88ce-392a-76d0-bd98-5be920ff6152" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019d88ce-392a-716f-85f1-2a79e5df04ca" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_AmendmentFlag_019d88ce-392a-716f-85f1-2a79e5df04ca" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019d88ce-392a-72aa-bb13-ddaaa79571ee" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityAddressesLineItems_019d88ce-392a-7026-83ae-20ffb46ac600" xlink:to="loc_dei_EntityCentralIndexKey_019d88ce-392a-72aa-bb13-ddaaa79571ee" xlink:type="arc" order="23"/>
  </link:definitionLink>
</link:linkbase>
