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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a0ee66-486b-7b0c-952b-ea6532a255d0,g:d411ddb3-ab84-4c56-826a-86c301572356-->
<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://bowheadspecialty.com/role/CondensedConsolidatedStatementsofChangesinMezzanineEquityandStockholdersEquityUnaudited" xlink:type="simple" xlink:href="bow-20260930.xsd#CondensedConsolidatedStatementsofChangesinMezzanineEquityandStockholdersEquityUnaudited"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/CondensedConsolidatedStatementsofChangesinMezzanineEquityandStockholdersEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_01a0ee66-4995-7619-bccd-9e29fa34fbac" 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_01a0ee66-4995-75c9-9532-0171831bcdfa" 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_01a0ee66-4995-7619-bccd-9e29fa34fbac" xlink:to="loc_us-gaap_StatementTable_01a0ee66-4995-75c9-9532-0171831bcdfa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_01a0ee66-4995-7416-86e0-76cab7b4c73b" 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_01a0ee66-4995-75c9-9532-0171831bcdfa" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_01a0ee66-4995-7416-86e0-76cab7b4c73b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0ee66-4995-7416-86e0-76cab7b4c73b_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_01a0ee66-4995-7416-86e0-76cab7b4c73b" xlink:to="loc_us-gaap_EquityComponentDomain_01a0ee66-4995-7416-86e0-76cab7b4c73b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a0ee66-4995-755a-8d4c-b444275aa548" 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_01a0ee66-4995-7416-86e0-76cab7b4c73b" xlink:to="loc_us-gaap_EquityComponentDomain_01a0ee66-4995-755a-8d4c-b444275aa548" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_01a0ee66-4995-74be-a002-17b2192cc31f" 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_01a0ee66-4995-755a-8d4c-b444275aa548" xlink:to="loc_us-gaap_CommonStockMember_01a0ee66-4995-74be-a002-17b2192cc31f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_01a0ee66-4995-7131-9fce-90ee9941daae" 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_01a0ee66-4995-755a-8d4c-b444275aa548" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_01a0ee66-4995-7131-9fce-90ee9941daae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a0ee66-4995-7847-a6ea-c41274333840" 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_01a0ee66-4995-755a-8d4c-b444275aa548" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a0ee66-4995-7847-a6ea-c41274333840" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_01a0ee66-4995-7178-aed1-d4f741a93bf7" 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_01a0ee66-4995-755a-8d4c-b444275aa548" xlink:to="loc_us-gaap_RetainedEarningsMember_01a0ee66-4995-7178-aed1-d4f741a93bf7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" 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_01a0ee66-4995-7619-bccd-9e29fa34fbac" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_01a0ee66-4995-7eda-9f5a-e7898a479f71" 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_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_01a0ee66-4995-7eda-9f5a-e7898a479f71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_01a0ee66-4995-71fc-a26f-3a435dd61c8b" 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_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_StockholdersEquity_01a0ee66-4995-71fc-a26f-3a435dd61c8b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_EquityAndTemporaryEquityAttributableToParent_01a0ee66-4995-7c10-9792-4e8d24f306ce" xlink:href="bow-20260930.xsd#bow_EquityAndTemporaryEquityAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_bow_EquityAndTemporaryEquityAttributableToParent_01a0ee66-4995-7c10-9792-4e8d24f306ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_01a0ee66-4995-7641-a59c-a7cefe6e404d" 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_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_NetIncomeLoss_01a0ee66-4995-7641-a59c-a7cefe6e404d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_01a0ee66-4995-7ee8-8aa4-85944549d810" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_01a0ee66-4995-7ee8-8aa4-85944549d810" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_01a0ee66-4995-7e2e-bcb2-7b62a29c18ed" 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_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_01a0ee66-4995-7e2e-bcb2-7b62a29c18ed" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_EquityAndTemporaryEquityShareBasedPaymentArrangementIncreaseForCostRecognition_01a0ee66-4995-7fff-8ee1-fb2cb7a3404e" xlink:href="bow-20260930.xsd#bow_EquityAndTemporaryEquityShareBasedPaymentArrangementIncreaseForCostRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_bow_EquityAndTemporaryEquityShareBasedPaymentArrangementIncreaseForCostRecognition_01a0ee66-4995-7fff-8ee1-fb2cb7a3404e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross_01a0ee66-4995-7d25-87c5-1c16d0cef78f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross_01a0ee66-4995-7d25-87c5-1c16d0cef78f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross_01a0ee66-4995-76a9-94b9-5e4e053af859" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross_01a0ee66-4995-76a9-94b9-5e4e053af859" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_01a0ee66-4995-77fc-88dc-513b22f03282" 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_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_01a0ee66-4995-77fc-88dc-513b22f03282" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_01a0ee66-4995-75b4-b815-d0aa7bc341c4" 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_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_01a0ee66-4995-75b4-b815-d0aa7bc341c4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued_01a0ee66-4995-7d04-bfbc-86f380d7d8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a0ee66-4995-7725-9e92-ab21aba1fd1e" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued_01a0ee66-4995-7d04-bfbc-86f380d7d8bc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_01a0ee66-4995-7c21-ad0f-adb81ef21079" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_01a0ee66-4995-79d1-acaa-5cf5632ae01c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_EquityAndTemporaryEquityAttributableToParent_01a0ee66-4995-7192-81de-53c05a9a906e" xlink:href="bow-20260930.xsd#bow_EquityAndTemporaryEquityAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_01a0ee66-4995-7526-920b-9e8a22efff82" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInTemporaryEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a0ee66-4995-7619-bccd-9e29fa34fbac" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_01a0ee66-4995-7526-920b-9e8a22efff82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_01a0ee66-4995-7c7b-9f62-868d0c47cd4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_01a0ee66-4995-7526-920b-9e8a22efff82" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_01a0ee66-4995-7c7b-9f62-868d0c47cd4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_TemporaryEquityShareBasedPaymentArrangementIncreaseForCostRecognition_01a0ee66-4995-7665-839d-5e912acd573c" xlink:href="bow-20260930.xsd#bow_TemporaryEquityShareBasedPaymentArrangementIncreaseForCostRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_01a0ee66-4995-7526-920b-9e8a22efff82" xlink:to="loc_bow_TemporaryEquityShareBasedPaymentArrangementIncreaseForCostRecognition_01a0ee66-4995-7665-839d-5e912acd573c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_01a0ee66-4995-7b4f-8b90-d15114ed2735" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/NatureofOperationsandSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#NatureofOperationsandSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/NatureofOperationsandSignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4995-7397-9af7-1b32b0942df2" 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_01a0ee66-4995-77ee-88dc-5e768124341f" 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_01a0ee66-4995-7397-9af7-1b32b0942df2" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a0ee66-4995-77ee-88dc-5e768124341f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_01a0ee66-4995-7241-aa6e-c8d5f9e136b4" 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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a0ee66-4995-77ee-88dc-5e768124341f" xlink:to="loc_srt_OwnershipAxis_01a0ee66-4995-7241-aa6e-c8d5f9e136b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_01a0ee66-4995-7241-aa6e-c8d5f9e136b4_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_01a0ee66-4995-7241-aa6e-c8d5f9e136b4" xlink:to="loc_srt_OwnershipDomain_01a0ee66-4995-7241-aa6e-c8d5f9e136b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_01a0ee66-4995-77dd-b9bd-34507bdcb43e" 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_01a0ee66-4995-7241-aa6e-c8d5f9e136b4" xlink:to="loc_srt_OwnershipDomain_01a0ee66-4995-77dd-b9bd-34507bdcb43e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AmFamMember_01a0ee66-4995-78ed-a729-1ce879ad5a23" xlink:href="bow-20260930.xsd#bow_AmFamMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_01a0ee66-4995-77dd-b9bd-34507bdcb43e" xlink:to="loc_bow_AmFamMember_01a0ee66-4995-78ed-a729-1ce879ad5a23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a0ee66-4995-78ef-a863-ff4f0339568b" 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_01a0ee66-4995-77ee-88dc-5e768124341f" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a0ee66-4995-78ef-a863-ff4f0339568b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a0ee66-4995-78ef-a863-ff4f0339568b_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_01a0ee66-4995-78ef-a863-ff4f0339568b" xlink:to="loc_us-gaap_RelatedPartyDomain_01a0ee66-4995-78ef-a863-ff4f0339568b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a0ee66-4995-7f91-ba9f-bdbb45baeb77" 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_01a0ee66-4995-78ef-a863-ff4f0339568b" xlink:to="loc_us-gaap_RelatedPartyDomain_01a0ee66-4995-7f91-ba9f-bdbb45baeb77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_01a0ee66-4995-7ca5-8b5d-d33c5697fad9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_01a0ee66-4995-7f91-ba9f-bdbb45baeb77" xlink:to="loc_us-gaap_RelatedPartyMember_01a0ee66-4995-7ca5-8b5d-d33c5697fad9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_01a0ee66-4995-7553-a8db-e217a1c44145" 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_01a0ee66-4995-77ee-88dc-5e768124341f" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_01a0ee66-4995-7553-a8db-e217a1c44145" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4995-7553-a8db-e217a1c44145_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_01a0ee66-4995-7553-a8db-e217a1c44145" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4995-7553-a8db-e217a1c44145_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4995-72ab-8ab6-e69686b7c3f3" 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_01a0ee66-4995-7553-a8db-e217a1c44145" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4995-72ab-8ab6-e69686b7c3f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AmFamMember_01a0ee66-4995-7945-8d63-162e09b1f356" xlink:href="bow-20260930.xsd#bow_AmFamMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4995-72ab-8ab6-e69686b7c3f3" xlink:to="loc_bow_AmFamMember_01a0ee66-4995-7945-8d63-162e09b1f356" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_RelatedPartyOwnershipInterest_01a0ee66-4995-779a-be23-41988f465a48" xlink:href="bow-20260930.xsd#bow_RelatedPartyOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4995-7397-9af7-1b32b0942df2" xlink:to="loc_bow_RelatedPartyOwnershipInterest_01a0ee66-4995-779a-be23-41988f465a48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_QuotaShareAgreementPercentage_01a0ee66-4995-726b-ba63-ddc3a9aa2590" xlink:href="bow-20260930.xsd#bow_QuotaShareAgreementPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4995-7397-9af7-1b32b0942df2" xlink:to="loc_bow_QuotaShareAgreementPercentage_01a0ee66-4995-726b-ba63-ddc3a9aa2590" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a15421-1472-722c-b02a-2145efabd113" 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_RelatedPartyTransactionLineItems_01a0ee66-4995-7397-9af7-1b32b0942df2" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a15421-1472-722c-b02a-2145efabd113" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_MergerConversionPricePerShare_01a159e9-8a40-7b83-9db5-bbf7828247d7" xlink:href="bow-20260930.xsd#bow_MergerConversionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4995-7397-9af7-1b32b0942df2" xlink:to="loc_bow_MergerConversionPricePerShare_01a159e9-8a40-7b83-9db5-bbf7828247d7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/InvestmentsScheduleofAmortizedCostandFairValueofFixedmaturitySecuritiesDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#InvestmentsScheduleofAmortizedCostandFairValueofFixedmaturitySecuritiesDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/InvestmentsScheduleofAmortizedCostandFairValueofFixedmaturitySecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7668-8642-d7667bbd3bb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7ae9-8c1e-95a382a93f60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7668-8642-d7667bbd3bb7" xlink:to="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7ae9-8c1e-95a382a93f60" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7040-b739-bd5164338c4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7ae9-8c1e-95a382a93f60" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7040-b739-bd5164338c4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7040-b739-bd5164338c4e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7040-b739-bd5164338c4e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7040-b739-bd5164338c4e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7040-b739-bd5164338c4e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7ca1-8626-e4312e0dd676" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7ca1-8626-e4312e0dd676" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7633-9e8c-3a65c416a0d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7633-9e8c-3a65c416a0d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-7348-83b8-750697cb167f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-7348-83b8-750697cb167f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7c5c-b46c-0c77887ac9d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7c5c-b46c-0c77887ac9d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-71af-a4d2-4dd4db3683fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-71af-a4d2-4dd4db3683fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7ae1-966a-5bc7b3227bbc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-77c5-b4ac-4db892617d9f" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7ae1-966a-5bc7b3227bbc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_01a0ee66-4995-7894-96c0-998f29f76fd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7668-8642-d7667bbd3bb7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_01a0ee66-4995-7894-96c0-998f29f76fd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_01a0ee66-4995-725b-929b-64920bb48937" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7668-8642-d7667bbd3bb7" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_01a0ee66-4995-725b-929b-64920bb48937" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_01a0ee66-4995-744c-9d6e-c8a15824c5b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7668-8642-d7667bbd3bb7" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_01a0ee66-4995-744c-9d6e-c8a15824c5b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_01a0ee66-4995-71cf-b37d-063ce1d2fcb2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7668-8642-d7667bbd3bb7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_01a0ee66-4995-71cf-b37d-063ce1d2fcb2" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/InvestmentsScheduleofContractualMaturityofFixedMaturitySecuritiesDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#InvestmentsScheduleofContractualMaturityofFixedMaturitySecuritiesDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/InvestmentsScheduleofContractualMaturityofFixedMaturitySecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-73e8-a7bc-68052ad6356a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7aae-9c38-57473aa7fb8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-73e8-a7bc-68052ad6356a" xlink:to="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7aae-9c38-57473aa7fb8c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7ada-9161-193ff1877af1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7aae-9c38-57473aa7fb8c" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7ada-9161-193ff1877af1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7ada-9161-193ff1877af1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7ada-9161-193ff1877af1" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7ada-9161-193ff1877af1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7cfd-a352-bcc4c2adcfc7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7ada-9161-193ff1877af1" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7cfd-a352-bcc4c2adcfc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-7a80-8c14-aaaebb54e212" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7cfd-a352-bcc4c2adcfc7" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-7a80-8c14-aaaebb54e212" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-78e6-8de5-b21fa2f0e2db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7cfd-a352-bcc4c2adcfc7" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-78e6-8de5-b21fa2f0e2db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7e99-82d8-769c7fed48d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7cfd-a352-bcc4c2adcfc7" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7e99-82d8-769c7fed48d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-73e8-a7bc-68052ad6356a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_01a0ee66-4995-7a83-994b-d21068b0b636" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_01a0ee66-4995-7a83-994b-d21068b0b636" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_01a0ee66-4995-7fc3-9b1f-d99b5e84ed4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_01a0ee66-4995-7fc3-9b1f-d99b5e84ed4a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_01a0ee66-4995-7e27-bf3a-8f1d674a1e1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_01a0ee66-4995-7e27-bf3a-8f1d674a1e1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_01a0ee66-4995-728e-b0dc-0af19e5ecf09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_01a0ee66-4995-728e-b0dc-0af19e5ecf09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_01a0ee66-4995-7493-b577-c1649c663c2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_01a0ee66-4995-7493-b577-c1649c663c2e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost_01a0ee66-4995-7e43-99e1-9b5082dbc30c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost_01a0ee66-4995-7e43-99e1-9b5082dbc30c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_01a0ee66-4995-7872-a826-311ab45425c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_01a0ee66-4995-722a-bf9a-dffc205de33a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss_01a0ee66-4995-7872-a826-311ab45425c3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-73e8-a7bc-68052ad6356a" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_01a0ee66-4995-7f92-bc83-1d3c59a24c15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_01a0ee66-4995-7f92-bc83-1d3c59a24c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_01a0ee66-4995-7794-9340-e6d3994617fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_01a0ee66-4995-7794-9340-e6d3994617fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_01a0ee66-4995-7172-ba17-d9707521521b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_01a0ee66-4995-7172-ba17-d9707521521b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_01a0ee66-4995-7574-8904-62cbccf8a8b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_01a0ee66-4995-7574-8904-62cbccf8a8b5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_01a0ee66-4995-7a20-9ee0-823bd94c1193" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_01a0ee66-4995-7a20-9ee0-823bd94c1193" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue_01a0ee66-4995-7e19-a685-6e44b174c4ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue_01a0ee66-4995-7e19-a685-6e44b174c4ff" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_01a0ee66-4995-7af4-92a5-3c6227106ae4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_01a0ee66-4995-7f9b-a036-5048c08e5ec9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_01a0ee66-4995-7af4-92a5-3c6227106ae4" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/InvestmentsScheduleofNetInvestmentIncomeDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#InvestmentsScheduleofNetInvestmentIncomeDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/InvestmentsScheduleofNetInvestmentIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7b27-8efa-152a46c58b7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7dbf-bcf6-82f145e0eba3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7b27-8efa-152a46c58b7b" xlink:to="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7dbf-bcf6-82f145e0eba3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7d07-96a5-58c0c6ae497c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7dbf-bcf6-82f145e0eba3" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7d07-96a5-58c0c6ae497c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7d07-96a5-58c0c6ae497c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7d07-96a5-58c0c6ae497c" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7d07-96a5-58c0c6ae497c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7d07-96a5-58c0c6ae497c" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7288-8bdc-39310235e07b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7288-8bdc-39310235e07b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-736a-bae5-4350c01cf150" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-736a-bae5-4350c01cf150" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-7ebb-8499-fff42e162c5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-7ebb-8499-fff42e162c5f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7f02-9989-21b190cc7499" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7f02-9989-21b190cc7499" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-742a-86a8-e08b1c868475" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-742a-86a8-e08b1c868475" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7707-a270-752e1db11295" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7707-a270-752e1db11295" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_01a0ee66-4995-7c5c-a092-97b06e498b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_01a0ee66-4995-7c5c-a092-97b06e498b9e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_01a0ee66-4995-72b3-9855-c5d961adfec8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7921-8d1a-b9fd10db1258" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_01a0ee66-4995-72b3-9855-c5d961adfec8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating_01a0ee66-4995-751a-9aa3-492fa4e1ec5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossInvestmentIncomeOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7b27-8efa-152a46c58b7b" xlink:to="loc_us-gaap_GrossInvestmentIncomeOperating_01a0ee66-4995-751a-9aa3-492fa4e1ec5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_01a0ee66-4995-7afa-a362-ca58e5a363cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7b27-8efa-152a46c58b7b" xlink:to="loc_us-gaap_InvestmentIncomeInvestmentExpense_01a0ee66-4995-7afa-a362-ca58e5a363cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_01a0ee66-4995-7130-b345-8dcc1c40b379" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-7b27-8efa-152a46c58b7b" xlink:to="loc_us-gaap_NetInvestmentIncome_01a0ee66-4995-7130-b345-8dcc1c40b379" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/InvestmentsScheduleofRestrictedAssetsDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#InvestmentsScheduleofRestrictedAssetsDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/InvestmentsScheduleofRestrictedAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76b0-a025-18dfe7f156b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-77ab-ad29-04039dfd11e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76b0-a025-18dfe7f156b9" xlink:to="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-77ab-ad29-04039dfd11e7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7345-9683-05fbde932835" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-77ab-ad29-04039dfd11e7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7345-9683-05fbde932835" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7345-9683-05fbde932835_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7345-9683-05fbde932835" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7345-9683-05fbde932835_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7345-9683-05fbde932835" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7c0f-a27f-9835078dd611" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7c0f-a27f-9835078dd611" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7647-aea1-86d54e257cf4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7647-aea1-86d54e257cf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-771d-9ece-c12b947af227" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-771d-9ece-c12b947af227" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7c51-b90e-6cfbdbb8eb63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7c51-b90e-6cfbdbb8eb63" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7639-8244-05f6f72692a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7639-8244-05f6f72692a4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7aa8-893c-b602219b51c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-76c1-a9cf-2af13bbab43f" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7aa8-893c-b602219b51c8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_RestrictedFixedMaturitySecurities_01a0ee66-4995-7f93-8eea-de96151c9965" xlink:href="bow-20260930.xsd#bow_RestrictedFixedMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76b0-a025-18dfe7f156b9" xlink:to="loc_bow_RestrictedFixedMaturitySecurities_01a0ee66-4995-7f93-8eea-de96151c9965" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_01a0ee66-4995-7ade-ae05-5d8b12d68658" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76b0-a025-18dfe7f156b9" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_01a0ee66-4995-7ade-ae05-5d8b12d68658" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedInvestments_01a0ee66-4995-74d3-b633-2e0f67024154" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76b0-a025-18dfe7f156b9" xlink:to="loc_us-gaap_RestrictedInvestments_01a0ee66-4995-74d3-b633-2e0f67024154" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/InvestmentsScheduleofGrossUnrealizedLossesDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#InvestmentsScheduleofGrossUnrealizedLossesDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/InvestmentsScheduleofGrossUnrealizedLossesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76d5-830d-c0c2ac115bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7773-88a2-fda89ecd75b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76d5-830d-c0c2ac115bcf" xlink:to="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7773-88a2-fda89ecd75b4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7c14-bd4b-704ec858af9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_01a0ee66-4995-7773-88a2-fda89ecd75b4" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7c14-bd4b-704ec858af9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7c14-bd4b-704ec858af9d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7c14-bd4b-704ec858af9d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7c14-bd4b-704ec858af9d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7c14-bd4b-704ec858af9d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7b47-b07d-96536320dcab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_01a0ee66-4995-7b47-b07d-96536320dcab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7a34-87cb-0f1dd1f97873" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7a34-87cb-0f1dd1f97873" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-798c-9cb5-d48a87d8f3e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-798c-9cb5-d48a87d8f3e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-794d-94ef-a2cd74153007" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-794d-94ef-a2cd74153007" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7a75-a9aa-ed85761a1c50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7a75-a9aa-ed85761a1c50" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-77a1-95e9-0c03feb7b722" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7103-ba75-8c753eebe656" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-77a1-95e9-0c03feb7b722" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_01a0ee66-4995-7110-b67a-bcc1d91db20e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76d5-830d-c0c2ac115bcf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_01a0ee66-4995-7110-b67a-bcc1d91db20e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_01a0ee66-4995-7291-96d3-2bf7e0445f77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_01a0ee66-4995-7110-b67a-bcc1d91db20e" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_01a0ee66-4995-7291-96d3-2bf7e0445f77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_01a0ee66-4995-7a6b-8d98-fd8c8ce2a3e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_01a0ee66-4995-7110-b67a-bcc1d91db20e" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_01a0ee66-4995-7a6b-8d98-fd8c8ce2a3e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_01a0ee66-4995-707b-94f2-55ec483f3aa8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_01a0ee66-4995-7110-b67a-bcc1d91db20e" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_01a0ee66-4995-707b-94f2-55ec483f3aa8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_01a0ee66-4995-79f2-8051-9d0281e70c04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_01a0ee66-4995-76d5-830d-c0c2ac115bcf" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_01a0ee66-4995-79f2-8051-9d0281e70c04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_01a0ee66-4995-7b71-9b32-8b6e09c63a49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_01a0ee66-4995-79f2-8051-9d0281e70c04" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_01a0ee66-4995-7b71-9b32-8b6e09c63a49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_01a0ee66-4995-763b-a801-39cd7b52aeae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_01a0ee66-4995-79f2-8051-9d0281e70c04" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_01a0ee66-4995-763b-a801-39cd7b52aeae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_01a0ee66-4995-76e1-a019-2b96e305fc96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_01a0ee66-4995-79f2-8051-9d0281e70c04" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_01a0ee66-4995-76e1-a019-2b96e305fc96" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/FairValueMeasurementsDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#FairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0ee66-4995-7ebf-8ffc-b53041984a83" 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_01a0ee66-4995-7728-ada6-179fce0747d7" 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_01a0ee66-4995-7ebf-8ffc-b53041984a83" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0ee66-4995-7728-ada6-179fce0747d7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0ee66-4995-7c12-8d3b-745dfe6589f2" 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_01a0ee66-4995-7728-ada6-179fce0747d7" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a0ee66-4995-7c12-8d3b-745dfe6589f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0ee66-4995-7c12-8d3b-745dfe6589f2_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_01a0ee66-4995-7c12-8d3b-745dfe6589f2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0ee66-4995-7c12-8d3b-745dfe6589f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0ee66-4995-78c4-9ad6-21af4e8744b2" 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_01a0ee66-4995-7c12-8d3b-745dfe6589f2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a0ee66-4995-78c4-9ad6-21af4e8744b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_01a0ee66-4995-758d-b47b-9927865e53b0" 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_01a0ee66-4995-78c4-9ad6-21af4e8744b2" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_01a0ee66-4995-758d-b47b-9927865e53b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_01a0ee66-4995-7557-b452-c67e2e40fd89" 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_01a0ee66-4995-78c4-9ad6-21af4e8744b2" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_01a0ee66-4995-7557-b452-c67e2e40fd89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_01a0ee66-4995-7d40-9df0-2bf371479adf" 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_01a0ee66-4995-78c4-9ad6-21af4e8744b2" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_01a0ee66-4995-7d40-9df0-2bf371479adf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7e3f-a568-02f82c7cd8a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a0ee66-4995-7728-ada6-179fce0747d7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7e3f-a568-02f82c7cd8a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7e3f-a568-02f82c7cd8a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7e3f-a568-02f82c7cd8a1" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7e3f-a568-02f82c7cd8a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a0ee66-4995-7e3f-a568-02f82c7cd8a1" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_01a0ee66-4995-7ac5-8514-290cc7000e8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_01a0ee66-4995-7ac5-8514-290cc7000e8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7025-970f-f7ca94007e37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_01a0ee66-4995-7025-970f-f7ca94007e37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-70bc-8e1e-b567326ef8ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_01a0ee66-4995-70bc-8e1e-b567326ef8ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7b3a-98bb-f3f3960eb50e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01a0ee66-4995-7b3a-98bb-f3f3960eb50e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7ad8-9bd9-db283f53bade" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_01a0ee66-4995-7ad8-9bd9-db283f53bade" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7ff6-bd32-ed957098bdf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a0ee66-4995-7301-a789-e9679fbf81e0" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_01a0ee66-4995-7ff6-bd32-ed957098bdf9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_01a0ee66-4995-75eb-9b00-8941befc8f08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0ee66-4995-7ebf-8ffc-b53041984a83" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_01a0ee66-4995-75eb-9b00-8941befc8f08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_01a0ee66-4995-7abb-9c58-592298a529c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a0ee66-4995-7ebf-8ffc-b53041984a83" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_01a0ee66-4995-7abb-9c58-592298a529c8" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/DeferredPolicyAcquisitionCostsScheduleofDeferredPolicyAcquisitionCostsActivityDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#DeferredPolicyAcquisitionCostsScheduleofDeferredPolicyAcquisitionCostsActivityDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/DeferredPolicyAcquisitionCostsScheduleofDeferredPolicyAcquisitionCostsActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostLineItems_01a0ee66-4995-7642-b285-e00f5b19988c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostTable_01a0ee66-4995-7eb0-a33e-d82ef3c27476" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredPolicyAcquisitionCostLineItems_01a0ee66-4995-7642-b285-e00f5b19988c" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostTable_01a0ee66-4995-7eb0-a33e-d82ef3c27476" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_01a0ee66-4995-7e83-945f-5c886942aeda" 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_DeferredPolicyAcquisitionCostTable_01a0ee66-4995-7eb0-a33e-d82ef3c27476" xlink:to="loc_srt_ProductOrServiceAxis_01a0ee66-4995-7e83-945f-5c886942aeda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7e83-945f-5c886942aeda_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_01a0ee66-4995-7e83-945f-5c886942aeda" xlink:to="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7e83-945f-5c886942aeda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-757b-87de-1123d66d5ee6" 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_01a0ee66-4995-7e83-945f-5c886942aeda" xlink:to="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-757b-87de-1123d66d5ee6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_BrokerCommissionMember_01a0ee66-4995-75c3-b802-c858c90a93a7" xlink:href="bow-20260930.xsd#bow_BrokerCommissionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-757b-87de-1123d66d5ee6" xlink:to="loc_bow_BrokerCommissionMember_01a0ee66-4995-75c3-b802-c858c90a93a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CedingFeesMember_01a0ee66-4995-7193-ba14-0835e444403c" xlink:href="bow-20260930.xsd#bow_CedingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-757b-87de-1123d66d5ee6" xlink:to="loc_bow_CedingFeesMember_01a0ee66-4995-7193-ba14-0835e444403c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_OtherDeferredPolicyAcquisitionCostsMember_01a0ee66-4995-73c8-947d-48fc1cc7fe53" xlink:href="bow-20260930.xsd#bow_OtherDeferredPolicyAcquisitionCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-757b-87de-1123d66d5ee6" xlink:to="loc_bow_OtherDeferredPolicyAcquisitionCostsMember_01a0ee66-4995-73c8-947d-48fc1cc7fe53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CedingCommissionMember_01a0ee66-4995-7e6e-b754-9da88b52e69e" xlink:href="bow-20260930.xsd#bow_CedingCommissionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-757b-87de-1123d66d5ee6" xlink:to="loc_bow_CedingCommissionMember_01a0ee66-4995-7e6e-b754-9da88b52e69e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredPolicyAcquisitionCostLineItems_01a0ee66-4995-7642-b285-e00f5b19988c" xlink:to="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCosts_01a0ee66-4995-76eb-97e2-9b50bf57b37a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCosts_01a0ee66-4995-76eb-97e2-9b50bf57b37a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostsAdditions_01a0ee66-4995-745d-8658-d7c5ec6c1807" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostsAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostsAdditions_01a0ee66-4995-745d-8658-d7c5ec6c1807" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_DeferredPolicyAcquisitionCostCedingCommission_01a0ee66-4995-78b6-89cc-61825c0ae397" xlink:href="bow-20260930.xsd#bow_DeferredPolicyAcquisitionCostCedingCommission"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:to="loc_bow_DeferredPolicyAcquisitionCostCedingCommission_01a0ee66-4995-78b6-89cc-61825c0ae397" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_TotalNetAdditions_01a0ee66-4995-7195-a41b-4db1d52848a8" xlink:href="bow-20260930.xsd#bow_TotalNetAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:to="loc_bow_TotalNetAdditions_01a0ee66-4995-7195-a41b-4db1d52848a8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_01a0ee66-4995-7d51-ab53-ab7e2089a7f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementAnalysisOfDeferredPolicyAcquisitionCostsRollForward_01a0ee66-4995-7d69-bab5-f07d17eb6f90" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_01a0ee66-4995-7d51-ab53-ab7e2089a7f7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCosts_01a0ee66-4995-71ee-991a-f1426a021888" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCosts"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/DeferredPolicyAcquisitionCostsScheduleofAmortizationofNetPolicyAcquisitionCostsDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#DeferredPolicyAcquisitionCostsScheduleofAmortizationofNetPolicyAcquisitionCostsDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/DeferredPolicyAcquisitionCostsScheduleofAmortizationofNetPolicyAcquisitionCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostLineItems_01a0ee66-4995-70f9-a926-7b2178e836ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostTable_01a0ee66-4995-7004-96ac-2180eedd7b95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredPolicyAcquisitionCostLineItems_01a0ee66-4995-70f9-a926-7b2178e836ae" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostTable_01a0ee66-4995-7004-96ac-2180eedd7b95" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_01a0ee66-4995-7e97-8018-58c6f4d941ab" 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_DeferredPolicyAcquisitionCostTable_01a0ee66-4995-7004-96ac-2180eedd7b95" xlink:to="loc_srt_ProductOrServiceAxis_01a0ee66-4995-7e97-8018-58c6f4d941ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7e97-8018-58c6f4d941ab_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_01a0ee66-4995-7e97-8018-58c6f4d941ab" xlink:to="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7e97-8018-58c6f4d941ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7c90-b6ca-58c6c795a4b1" 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_01a0ee66-4995-7e97-8018-58c6f4d941ab" xlink:to="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7c90-b6ca-58c6c795a4b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_BrokerCommissionMember_01a0ee66-4995-7439-ab26-8b9b6f0fb91e" xlink:href="bow-20260930.xsd#bow_BrokerCommissionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7c90-b6ca-58c6c795a4b1" xlink:to="loc_bow_BrokerCommissionMember_01a0ee66-4995-7439-ab26-8b9b6f0fb91e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CedingFeesMember_01a0ee66-4995-7714-b436-02d843cfd8ec" xlink:href="bow-20260930.xsd#bow_CedingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7c90-b6ca-58c6c795a4b1" xlink:to="loc_bow_CedingFeesMember_01a0ee66-4995-7714-b436-02d843cfd8ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_OtherDeferredPolicyAcquisitionCostsMember_01a0ee66-4995-7e19-94f0-92a424d2ada5" xlink:href="bow-20260930.xsd#bow_OtherDeferredPolicyAcquisitionCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7c90-b6ca-58c6c795a4b1" xlink:to="loc_bow_OtherDeferredPolicyAcquisitionCostsMember_01a0ee66-4995-7e19-94f0-92a424d2ada5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CedingCommissionMember_01a0ee66-4995-767b-9fc7-f472c2549b84" xlink:href="bow-20260930.xsd#bow_CedingCommissionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a0ee66-4995-7c90-b6ca-58c6c795a4b1" xlink:to="loc_bow_CedingCommissionMember_01a0ee66-4995-767b-9fc7-f472c2549b84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_01a0ee66-4995-7a93-ab8b-db8d651cc148" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredPolicyAcquisitionCostLineItems_01a0ee66-4995-70f9-a926-7b2178e836ae" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_01a0ee66-4995-7a93-ab8b-db8d651cc148" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/PremiumsandReinsuranceRelatedInformationNarrativeDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#PremiumsandReinsuranceRelatedInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/PremiumsandReinsuranceRelatedInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectsOfReinsuranceLineItems_01a0ee66-4996-70ff-8971-36902229afa5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectsOfReinsuranceLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_01a0ee66-4996-7a74-9d00-d476485458dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_01a0ee66-4996-70ff-8971-36902229afa5" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_01a0ee66-4996-7a74-9d00-d476485458dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a0ee66-4996-71a7-8269-848d2a48c2a1" 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_ScheduleOfDefinedBenefitPlansDisclosuresTable_01a0ee66-4996-7a74-9d00-d476485458dd" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a0ee66-4996-71a7-8269-848d2a48c2a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-71a7-8269-848d2a48c2a1_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_01a0ee66-4996-71a7-8269-848d2a48c2a1" xlink:to="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-71a7-8269-848d2a48c2a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7e19-a1d1-412892aae051" 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_01a0ee66-4996-71a7-8269-848d2a48c2a1" xlink:to="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7e19-a1d1-412892aae051" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_01a0ee66-4996-7048-86fb-39ffb85987b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7e19-a1d1-412892aae051" xlink:to="loc_us-gaap_RelatedPartyMember_01a0ee66-4996-7048-86fb-39ffb85987b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededPremiumsWritten_01a0ee66-4996-7122-812e-2e6051301d7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededPremiumsWritten"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_01a0ee66-4996-70ff-8971-36902229afa5" xlink:to="loc_us-gaap_CededPremiumsWritten_01a0ee66-4996-7122-812e-2e6051301d7a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededPremiumsEarned_01a0ee66-4996-710f-a312-7c99b27fd781" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededPremiumsEarned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_01a0ee66-4996-70ff-8971-36902229afa5" xlink:to="loc_us-gaap_CededPremiumsEarned_01a0ee66-4996-710f-a312-7c99b27fd781" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded_01a0ee66-4996-7860-8467-f7099b85c78e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_01a0ee66-4996-70ff-8971-36902229afa5" xlink:to="loc_us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded_01a0ee66-4996-7860-8467-f7099b85c78e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses_01a0ee66-4996-7023-993b-1e0a5f1efe1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectsOfReinsuranceLineItems_01a0ee66-4996-70ff-8971-36902229afa5" xlink:to="loc_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses_01a0ee66-4996-7023-993b-1e0a5f1efe1b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/PremiumsandReinsuranceRelatedInformationScheduleofAMBestFinancialStrengthRatingandPercentofTotalReinsuranceRecoverableDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#PremiumsandReinsuranceRelatedInformationScheduleofAMBestFinancialStrengthRatingandPercentofTotalReinsuranceRecoverableDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/PremiumsandReinsuranceRelatedInformationScheduleofAMBestFinancialStrengthRatingandPercentofTotalReinsuranceRecoverableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskLineItems_01a0ee66-4996-7a78-a7cc-913ebb0ce615" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskTable_01a0ee66-4996-7ab9-a43d-56cf289c953a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CededCreditRiskLineItems_01a0ee66-4996-7a78-a7cc-913ebb0ce615" xlink:to="loc_us-gaap_CededCreditRiskTable_01a0ee66-4996-7ab9-a43d-56cf289c953a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4996-7c51-bf96-ac364773c36b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_01a0ee66-4996-7ab9-a43d-56cf289c953a" xlink:to="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4996-7c51-bf96-ac364773c36b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-7c51-bf96-ac364773c36b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskReinsurerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4996-7c51-bf96-ac364773c36b" xlink:to="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-7c51-bf96-ac364773c36b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskReinsurerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4996-7c51-bf96-ac364773c36b" xlink:to="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_RenaissanceReinsuranceU.S.IncMember_01a0ee66-4996-79d2-a352-714047cc902f" xlink:href="bow-20260930.xsd#bow_RenaissanceReinsuranceU.S.IncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:to="loc_bow_RenaissanceReinsuranceU.S.IncMember_01a0ee66-4996-79d2-a352-714047cc902f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_EnduranceAssuranceCorporationMember_01a0ee66-4996-79f4-8b02-1ddbdfcab033" xlink:href="bow-20260930.xsd#bow_EnduranceAssuranceCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:to="loc_bow_EnduranceAssuranceCorporationMember_01a0ee66-4996-79f4-8b02-1ddbdfcab033" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_MarkelGlobalReinsuranceCompanyMember_01a0ee66-4996-7c58-8539-79b27476a12e" xlink:href="bow-20260930.xsd#bow_MarkelGlobalReinsuranceCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:to="loc_bow_MarkelGlobalReinsuranceCompanyMember_01a0ee66-4996-7c58-8539-79b27476a12e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AscotBermudaLimitedMember_01a0ee66-4996-7288-aa45-a06a346341c9" xlink:href="bow-20260930.xsd#bow_AscotBermudaLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:to="loc_bow_AscotBermudaLimitedMember_01a0ee66-4996-7288-aa45-a06a346341c9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AmericanFamilyConnectPropertyAndCasualtyInsuranceCompanyMember_01a0ee66-4996-7995-ac96-b001596ca840" xlink:href="bow-20260930.xsd#bow_AmericanFamilyConnectPropertyAndCasualtyInsuranceCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:to="loc_bow_AmericanFamilyConnectPropertyAndCasualtyInsuranceCompanyMember_01a0ee66-4996-7995-ac96-b001596ca840" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReinsurerMember_01a0ee66-4996-7083-b7e8-998fd35f1797" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherReinsurerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4996-76c8-b969-0f8d2d15f014" xlink:to="loc_us-gaap_OtherReinsurerMember_01a0ee66-4996-7083-b7e8-998fd35f1797" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestAxis_01a0ee66-4996-726c-bd56-391d80681e65" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_01a0ee66-4996-7ab9-a43d-56cf289c953a" xlink:to="loc_srt_CreditRatingAMBestAxis_01a0ee66-4996-726c-bd56-391d80681e65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestDomain_01a0ee66-4996-726c-bd56-391d80681e65_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CreditRatingAMBestAxis_01a0ee66-4996-726c-bd56-391d80681e65" xlink:to="loc_srt_CreditRatingAMBestDomain_01a0ee66-4996-726c-bd56-391d80681e65_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestDomain_01a0ee66-4996-7b5f-b97a-824f266aa2bb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CreditRatingAMBestAxis_01a0ee66-4996-726c-bd56-391d80681e65" xlink:to="loc_srt_CreditRatingAMBestDomain_01a0ee66-4996-7b5f-b97a-824f266aa2bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AMBestAPlusRatingMember_01a0ee66-4996-7934-bc9a-948cb517eb5b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AMBestAPlusRatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CreditRatingAMBestDomain_01a0ee66-4996-7b5f-b97a-824f266aa2bb" xlink:to="loc_srt_AMBestAPlusRatingMember_01a0ee66-4996-7934-bc9a-948cb517eb5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AMBestARatingMember_01a0ee66-4996-78d7-a710-91309d7589b1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AMBestARatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CreditRatingAMBestDomain_01a0ee66-4996-7b5f-b97a-824f266aa2bb" xlink:to="loc_srt_AMBestARatingMember_01a0ee66-4996-78d7-a710-91309d7589b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4996-7d43-bb89-51ec9fce93e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_01a0ee66-4996-7ab9-a43d-56cf289c953a" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4996-7d43-bb89-51ec9fce93e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4996-7d43-bb89-51ec9fce93e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4996-7d43-bb89-51ec9fce93e1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4996-7d43-bb89-51ec9fce93e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4996-7746-a9ac-c69129e4f128" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4996-7d43-bb89-51ec9fce93e1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4996-7746-a9ac-c69129e4f128" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverableMember_01a0ee66-4996-7018-be4b-fecf29e9a873" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4996-7746-a9ac-c69129e4f128" xlink:to="loc_us-gaap_ReinsuranceRecoverableMember_01a0ee66-4996-7018-be4b-fecf29e9a873" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4996-79b1-9902-4beff3098b60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_01a0ee66-4996-7ab9-a43d-56cf289c953a" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4996-79b1-9902-4beff3098b60" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4996-79b1-9902-4beff3098b60_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4996-79b1-9902-4beff3098b60" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4996-79b1-9902-4beff3098b60_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4996-71fc-ba3c-bcb1f9e66e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4996-79b1-9902-4beff3098b60" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4996-71fc-ba3c-bcb1f9e66e4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsurerConcentrationRiskMember_01a0ee66-4996-72ee-a5f3-736d78942020" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsurerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4996-71fc-ba3c-bcb1f9e66e4d" xlink:to="loc_us-gaap_ReinsurerConcentrationRiskMember_01a0ee66-4996-72ee-a5f3-736d78942020" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_01a0ee66-4996-7b5d-8678-741ec1aad924" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskLineItems_01a0ee66-4996-7a78-a7cc-913ebb0ce615" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_01a0ee66-4996-7b5d-8678-741ec1aad924" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/DebtandFinancingArrangementsDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#DebtandFinancingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/DebtandFinancingArrangementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_01a0ee66-4996-7d67-884c-2e6c304dea83" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_01a0ee66-4996-7d67-884c-2e6c304dea83" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_01a0ee66-4996-7a1e-96ee-f939a11e5a90" 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_LineOfCreditFacilityTable_01a0ee66-4996-7d67-884c-2e6c304dea83" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_01a0ee66-4996-7a1e-96ee-f939a11e5a90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a0ee66-4996-7a1e-96ee-f939a11e5a90_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_01a0ee66-4996-7a1e-96ee-f939a11e5a90" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a0ee66-4996-7a1e-96ee-f939a11e5a90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a0ee66-4996-7206-bb22-0f77f8488807" 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_01a0ee66-4996-7a1e-96ee-f939a11e5a90" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a0ee66-4996-7206-bb22-0f77f8488807" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_01a0ee66-4996-778d-9a31-ee016178d5ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_01a0ee66-4996-7206-bb22-0f77f8488807" xlink:to="loc_us-gaap_SeniorNotesMember_01a0ee66-4996-778d-9a31-ee016178d5ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_01a0ee66-4996-70ec-a0dd-13e181ed1be2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_01a0ee66-4996-7206-bb22-0f77f8488807" xlink:to="loc_us-gaap_LineOfCreditMember_01a0ee66-4996-70ec-a0dd-13e181ed1be2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_01a0ee66-4996-727f-852b-d400c48a6158" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_01a0ee66-4996-7d67-884c-2e6c304dea83" xlink:to="loc_us-gaap_DebtInstrumentAxis_01a0ee66-4996-727f-852b-d400c48a6158" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-727f-852b-d400c48a6158_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a0ee66-4996-727f-852b-d400c48a6158" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-727f-852b-d400c48a6158_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-7737-957f-9e04f8dc2fa3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a0ee66-4996-727f-852b-d400c48a6158" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-7737-957f-9e04f8dc2fa3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_A7.75SeniorNotesMember_01a0ee66-4996-7229-94f6-34b4f72ac0be" xlink:href="bow-20260930.xsd#bow_A7.75SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-7737-957f-9e04f8dc2fa3" xlink:to="loc_bow_A7.75SeniorNotesMember_01a0ee66-4996-7229-94f6-34b4f72ac0be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_A2024CreditAgreementMember_01a0ee66-4996-74d2-af1f-2edebc015cb5" xlink:href="bow-20260930.xsd#bow_A2024CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-7737-957f-9e04f8dc2fa3" xlink:to="loc_bow_A2024CreditAgreementMember_01a0ee66-4996-74d2-af1f-2edebc015cb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_A2025CreditAgreementMember_01a0ee66-4996-7a18-8c30-cd44cb7319ba" xlink:href="bow-20260930.xsd#bow_A2025CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_01a0ee66-4996-7737-957f-9e04f8dc2fa3" xlink:to="loc_bow_A2025CreditAgreementMember_01a0ee66-4996-7a18-8c30-cd44cb7319ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_01a0ee66-4996-7129-bd1e-ec1e8f9d8539" 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_LineOfCreditFacilityTable_01a0ee66-4996-7d67-884c-2e6c304dea83" xlink:to="loc_us-gaap_CreditFacilityAxis_01a0ee66-4996-7129-bd1e-ec1e8f9d8539" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_01a0ee66-4996-7129-bd1e-ec1e8f9d8539_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_01a0ee66-4996-7129-bd1e-ec1e8f9d8539" xlink:to="loc_us-gaap_CreditFacilityDomain_01a0ee66-4996-7129-bd1e-ec1e8f9d8539_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_01a0ee66-4996-77f2-8711-ed91d659c4d5" 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_01a0ee66-4996-7129-bd1e-ec1e8f9d8539" xlink:to="loc_us-gaap_CreditFacilityDomain_01a0ee66-4996-77f2-8711-ed91d659c4d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_01a0ee66-4996-7897-bd68-969f505c58bf" 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_CreditFacilityDomain_01a0ee66-4996-77f2-8711-ed91d659c4d5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_01a0ee66-4996-7897-bd68-969f505c58bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_01a0ee66-4996-7eb7-b51c-2e6559650060" 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_01a0ee66-4996-77f2-8711-ed91d659c4d5" xlink:to="loc_us-gaap_LetterOfCreditMember_01a0ee66-4996-7eb7-b51c-2e6559650060" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_01a0ee66-4996-78d0-a861-20c47e23d342" 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_LineOfCreditFacilityTable_01a0ee66-4996-7d67-884c-2e6c304dea83" xlink:to="loc_us-gaap_VariableRateAxis_01a0ee66-4996-78d0-a861-20c47e23d342" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_01a0ee66-4996-78d0-a861-20c47e23d342_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_01a0ee66-4996-78d0-a861-20c47e23d342" xlink:to="loc_us-gaap_VariableRateDomain_01a0ee66-4996-78d0-a861-20c47e23d342_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_01a0ee66-4996-795c-9aac-62e1b2b9f1b4" 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_01a0ee66-4996-78d0-a861-20c47e23d342" xlink:to="loc_us-gaap_VariableRateDomain_01a0ee66-4996-795c-9aac-62e1b2b9f1b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_NewYorkFederalReserveBankRateMember_01a0ee66-4996-7a67-a5a2-6e787c179ed9" xlink:href="bow-20260930.xsd#bow_NewYorkFederalReserveBankRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_01a0ee66-4996-795c-9aac-62e1b2b9f1b4" xlink:to="loc_bow_NewYorkFederalReserveBankRateMember_01a0ee66-4996-7a67-a5a2-6e787c179ed9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_01a0ee66-4996-73c9-9a16-353cbe0f3773" 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_01a0ee66-4996-795c-9aac-62e1b2b9f1b4" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_01a0ee66-4996-73c9-9a16-353cbe0f3773" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_01a0ee66-4996-7e1d-ab78-ac1e2332ef5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_01a0ee66-4996-7e1d-ab78-ac1e2332ef5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_01a0ee66-4996-7bff-ae7d-5e3dbd033cc6" 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_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_01a0ee66-4996-7bff-ae7d-5e3dbd033cc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfDebt_01a0ee66-4996-71a8-acec-b46a43e38b9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfDebt_01a0ee66-4996-71a8-acec-b46a43e38b9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_01a0ee66-4996-78e0-8de9-e254d08dcb44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_LongTermDebt_01a0ee66-4996-78e0-8de9-e254d08dcb44" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_01a0ee66-4996-7a8b-a92f-155a7af09270" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_01a0ee66-4996-7a8b-a92f-155a7af09270" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_01a0ee66-4996-7604-abbc-8f05dc0fb6bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_InterestExpenseDebt_01a0ee66-4996-7604-abbc-8f05dc0fb6bf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a0ee66-4996-78bd-b695-f857ea3c8df5" 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_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a0ee66-4996-78bd-b695-f857ea3c8df5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_01a0ee66-4996-7b57-87f6-f24e2d819ae0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_01a0ee66-4996-7bbb-ad5d-a4356801cc6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_01a0ee66-4996-7bbb-ad5d-a4356801cc6f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_LineOfCreditFacilityAccordionFeatureIncreaseLimit_01a0ee66-4996-720f-a2e3-7ed29affd41a" xlink:href="bow-20260930.xsd#bow_LineOfCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_bow_LineOfCreditFacilityAccordionFeatureIncreaseLimit_01a0ee66-4996-720f-a2e3-7ed29affd41a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_01a0ee66-4996-740d-b920-e9a2c7bc3db5" 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_LineOfCreditFacilityLineItems_01a0ee66-4996-7ed3-8863-d5543a9a3286" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_01a0ee66-4996-740d-b920-e9a2c7bc3db5" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/StockBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#StockBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/StockBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" 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_01a0ee66-4996-792c-89ce-a626cb3af4b7" 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_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-792c-89ce-a626cb3af4b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_01a0ee66-4996-7f7c-bdf0-537bcb83bd3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-792c-89ce-a626cb3af4b7" xlink:to="loc_us-gaap_PlanNameAxis_01a0ee66-4996-7f7c-bdf0-537bcb83bd3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_01a0ee66-4996-7f7c-bdf0-537bcb83bd3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_01a0ee66-4996-7f7c-bdf0-537bcb83bd3e" xlink:to="loc_us-gaap_PlanNameDomain_01a0ee66-4996-7f7c-bdf0-537bcb83bd3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_01a0ee66-4996-7df2-870a-904aa052c4e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_01a0ee66-4996-7f7c-bdf0-537bcb83bd3e" xlink:to="loc_us-gaap_PlanNameDomain_01a0ee66-4996-7df2-870a-904aa052c4e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_A2024PlanMember_01a0ee66-4996-730e-af21-502550397841" xlink:href="bow-20260930.xsd#bow_A2024PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_01a0ee66-4996-7df2-870a-904aa052c4e5" xlink:to="loc_bow_A2024PlanMember_01a0ee66-4996-730e-af21-502550397841" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-71a6-919c-d6e6be6dbe0a" 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_01a0ee66-4996-792c-89ce-a626cb3af4b7" xlink:to="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-71a6-919c-d6e6be6dbe0a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-71a6-919c-d6e6be6dbe0a_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_01a0ee66-4996-71a6-919c-d6e6be6dbe0a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-71a6-919c-d6e6be6dbe0a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7dcf-95ef-5a29117ec454" 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_01a0ee66-4996-71a6-919c-d6e6be6dbe0a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7dcf-95ef-5a29117ec454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0ee66-4996-750e-aba6-2db2727f182a" 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_01a0ee66-4996-7dcf-95ef-5a29117ec454" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0ee66-4996-750e-aba6-2db2727f182a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7972-92d9-1e4199409f9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7dcf-95ef-5a29117ec454" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7972-92d9-1e4199409f9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_01a0ee66-4996-7445-943f-f8319e8472a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7dcf-95ef-5a29117ec454" xlink:to="loc_us-gaap_WarrantMember_01a0ee66-4996-7445-943f-f8319e8472a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_OverallotmentWarrantsMember_01a0ee66-4996-7656-8f5d-c4b431d91b42" xlink:href="bow-20260930.xsd#bow_OverallotmentWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WarrantMember_01a0ee66-4996-7445-943f-f8319e8472a7" xlink:to="loc_bow_OverallotmentWarrantsMember_01a0ee66-4996-7656-8f5d-c4b431d91b42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_01a0ee66-4996-705f-b7ed-c3523723018d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-792c-89ce-a626cb3af4b7" xlink:to="loc_us-gaap_VestingAxis_01a0ee66-4996-705f-b7ed-c3523723018d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_01a0ee66-4996-705f-b7ed-c3523723018d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_01a0ee66-4996-705f-b7ed-c3523723018d" xlink:to="loc_us-gaap_VestingDomain_01a0ee66-4996-705f-b7ed-c3523723018d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_01a0ee66-4996-7298-9578-e38efbe413f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_01a0ee66-4996-705f-b7ed-c3523723018d" xlink:to="loc_us-gaap_VestingDomain_01a0ee66-4996-7298-9578-e38efbe413f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_01a0ee66-4996-7cd4-8e48-eec0a867699c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_01a0ee66-4996-7298-9578-e38efbe413f3" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_01a0ee66-4996-7cd4-8e48-eec0a867699c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_01a0ee66-4996-792d-a45c-ba28a4b70728" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_01a0ee66-4996-7298-9578-e38efbe413f3" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_01a0ee66-4996-792d-a45c-ba28a4b70728" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a0ee66-4996-7a5f-a748-6e66167c0981" 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_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-792c-89ce-a626cb3af4b7" xlink:to="loc_srt_RangeAxis_01a0ee66-4996-7a5f-a748-6e66167c0981" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0ee66-4996-7a5f-a748-6e66167c0981_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_01a0ee66-4996-7a5f-a748-6e66167c0981" xlink:to="loc_srt_RangeMember_01a0ee66-4996-7a5f-a748-6e66167c0981_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a0ee66-4996-702a-81db-f829ae5a99eb" 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_01a0ee66-4996-7a5f-a748-6e66167c0981" xlink:to="loc_srt_RangeMember_01a0ee66-4996-702a-81db-f829ae5a99eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a0ee66-4996-7619-a244-f79488e89888" 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_01a0ee66-4996-702a-81db-f829ae5a99eb" xlink:to="loc_srt_MinimumMember_01a0ee66-4996-7619-a244-f79488e89888" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a0ee66-4996-7e5c-9f83-987ac4ae9c38" 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_01a0ee66-4996-702a-81db-f829ae5a99eb" xlink:to="loc_srt_MaximumMember_01a0ee66-4996-7e5c-9f83-987ac4ae9c38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_01a0ee66-4996-7635-9a32-c1d5993752cd" 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_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_01a0ee66-4996-7635-9a32-c1d5993752cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedIncreasedPercent_01a0ee66-4996-70e9-ad8f-77a635354601" xlink:href="bow-20260930.xsd#bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedIncreasedPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedIncreasedPercent_01a0ee66-4996-70e9-ad8f-77a635354601" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-7101-b8f8-0b185b24c480" 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_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-7101-b8f8-0b185b24c480" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-71ae-9c40-ddcf9cc836b0" 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_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-71ae-9c40-ddcf9cc836b0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_01a0ee66-4996-74bc-9a5f-6d8e9722ebd1" 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_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_01a0ee66-4996-74bc-9a5f-6d8e9722ebd1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_01a0ee66-4996-7306-8c72-2497bff43ca0" 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_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_01a0ee66-4996-7306-8c72-2497bff43ca0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a0ee66-4996-7e65-a139-65f123f75d2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a0ee66-4996-7e65-a139-65f123f75d2b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_01a0ee66-4996-7ebd-a87b-50a6c9b7d317" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_01a0ee66-4996-7ebd-a87b-50a6c9b7d317" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0ee66-4996-7a31-b850-2322f30a179d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a0ee66-4996-7a31-b850-2322f30a179d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesEarnedPercent_01a0ee66-4996-7134-aba0-dcf8868e1dd8" xlink:href="bow-20260930.xsd#bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesEarnedPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesEarnedPercent_01a0ee66-4996-7134-aba0-dcf8868e1dd8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_SaleOfStockThresholdConsecutiveTradingDays_01a0ee66-4996-7afd-9b3d-cb996c8d3ea3" xlink:href="bow-20260930.xsd#bow_SaleOfStockThresholdConsecutiveTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_bow_SaleOfStockThresholdConsecutiveTradingDays_01a0ee66-4996-7afd-9b3d-cb996c8d3ea3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_01a0ee66-4996-797f-9b15-737cc31b43df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_01a0ee66-4996-797f-9b15-737cc31b43df" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValuePerShare_01a0ee66-4996-794d-9f12-779488e92863" xlink:href="bow-20260930.xsd#bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValuePerShare_01a0ee66-4996-794d-9f12-779488e92863" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisePrice_01a0ee66-4996-70c1-ba73-9450063635d2" xlink:href="bow-20260930.xsd#bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisePrice_01a0ee66-4996-70c1-ba73-9450063635d2" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardExercisePeriod_01a0ee66-4996-775c-886c-3eb4324411a0" xlink:href="bow-20260930.xsd#bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardExercisePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_bow_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardExercisePeriod_01a0ee66-4996-775c-886c-3eb4324411a0" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0ee66-4996-74dd-8830-1eb01a8fdcf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0ee66-4996-74dd-8830-1eb01a8fdcf3" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised_01a0ee66-4996-7c33-a163-9044ad054d6e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7ee6-a0f7-b10726505ce4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised_01a0ee66-4996-7c33-a163-9044ad054d6e" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofRSUActivityDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#StockBasedCompensationScheduleofRSUActivityDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofRSUActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7f0c-8f65-1d540fd8f752" 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_01a0ee66-4996-7a03-902e-48d054087007" 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_01a0ee66-4996-7f0c-8f65-1d540fd8f752" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-7a03-902e-48d054087007" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-7f60-b093-62563709c97d" 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_01a0ee66-4996-7a03-902e-48d054087007" xlink:to="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-7f60-b093-62563709c97d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7f60-b093-62563709c97d_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_01a0ee66-4996-7f60-b093-62563709c97d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7f60-b093-62563709c97d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-702e-b25c-74441c67bbea" 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_01a0ee66-4996-7f60-b093-62563709c97d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-702e-b25c-74441c67bbea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0ee66-4996-7107-81a4-06c02016172a" 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_01a0ee66-4996-702e-b25c-74441c67bbea" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0ee66-4996-7107-81a4-06c02016172a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7b0c-9718-fbe6b0e1a41a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7f0c-8f65-1d540fd8f752" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7b0c-9718-fbe6b0e1a41a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0ee66-4996-7f84-af81-cf3e496de15f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7b0c-9718-fbe6b0e1a41a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0ee66-4996-7f84-af81-cf3e496de15f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-73de-afbf-2dd4579e1900" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7b0c-9718-fbe6b0e1a41a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-73de-afbf-2dd4579e1900" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0ee66-4996-7bf6-8eaf-a9431cb6e1cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7b0c-9718-fbe6b0e1a41a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0ee66-4996-7bf6-8eaf-a9431cb6e1cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0ee66-4996-76fb-baff-ec2574315916" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7b0c-9718-fbe6b0e1a41a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0ee66-4996-76fb-baff-ec2574315916" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0ee66-4996-7125-bb7e-9b20153137f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7f72-903c-30979e35926e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-7f0c-8f65-1d540fd8f752" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7f72-903c-30979e35926e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-7065-b9ca-47ef0d36fab7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7f72-903c-30979e35926e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-7065-b9ca-47ef0d36fab7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-7265-b6c1-0fcec5008fbf" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7f72-903c-30979e35926e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-7265-b6c1-0fcec5008fbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-7db0-9f49-f3e656e90f96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7f72-903c-30979e35926e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-7db0-9f49-f3e656e90f96" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0ee66-4996-7195-9c95-e1742621a770" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7f72-903c-30979e35926e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0ee66-4996-7195-9c95-e1742621a770" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-7df6-a775-359e7a805ec0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofTheNumberofPSUsEarnedDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#StockBasedCompensationScheduleofTheNumberofPSUsEarnedDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofTheNumberofPSUsEarnedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-703f-8505-76164d360b77" 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_01a0ee66-4996-75c9-8a6e-763961d869de" 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_01a0ee66-4996-703f-8505-76164d360b77" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-75c9-8a6e-763961d869de" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-751e-b57c-78434641c471" 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_01a0ee66-4996-75c9-8a6e-763961d869de" xlink:to="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-751e-b57c-78434641c471" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-751e-b57c-78434641c471_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_01a0ee66-4996-751e-b57c-78434641c471" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-751e-b57c-78434641c471_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79b0-8584-2c958ffe2c53" 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_01a0ee66-4996-751e-b57c-78434641c471" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79b0-8584-2c958ffe2c53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7aae-a742-67ab7058f076" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79b0-8584-2c958ffe2c53" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7aae-a742-67ab7058f076" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-7fd3-9ea5-0dd2feac5373" 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_01a0ee66-4996-703f-8505-76164d360b77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-7fd3-9ea5-0dd2feac5373" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-73aa-b4ca-74ba249714e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-703f-8505-76164d360b77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-73aa-b4ca-74ba249714e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_01a0ee66-4996-71b7-87c6-c551234cc7db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-703f-8505-76164d360b77" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_01a0ee66-4996-71b7-87c6-c551234cc7db" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofPSUActivityDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#StockBasedCompensationScheduleofPSUActivityDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofPSUActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-703a-aa4c-7b77722629e9" 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_01a0ee66-4996-7d88-9a66-3ee255ae9d08" 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_01a0ee66-4996-703a-aa4c-7b77722629e9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-7d88-9a66-3ee255ae9d08" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-7afe-ad40-06f453348e36" 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_01a0ee66-4996-7d88-9a66-3ee255ae9d08" xlink:to="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-7afe-ad40-06f453348e36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7afe-ad40-06f453348e36_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_01a0ee66-4996-7afe-ad40-06f453348e36" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7afe-ad40-06f453348e36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7845-a5ac-44b23067a609" 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_01a0ee66-4996-7afe-ad40-06f453348e36" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7845-a5ac-44b23067a609" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7285-8548-cb1dcb7d65d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7845-a5ac-44b23067a609" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7285-8548-cb1dcb7d65d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7194-839e-1756fa00b99f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-703a-aa4c-7b77722629e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7194-839e-1756fa00b99f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0ee66-4996-7439-a6ab-7f5c5656d1a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7194-839e-1756fa00b99f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0ee66-4996-7439-a6ab-7f5c5656d1a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-73e5-814a-13a7ad1146b6" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7194-839e-1756fa00b99f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a0ee66-4996-73e5-814a-13a7ad1146b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0ee66-4996-73bf-bd0a-c8daa12550dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7194-839e-1756fa00b99f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a0ee66-4996-73bf-bd0a-c8daa12550dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0ee66-4996-7cca-8d52-3aed716438df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a0ee66-4996-7194-839e-1756fa00b99f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a0ee66-4996-7cca-8d52-3aed716438df" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a0ee66-4996-743e-ba23-4de137fe3bfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7ea3-917a-7bc5f6f77ab2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-703a-aa4c-7b77722629e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7ea3-917a-7bc5f6f77ab2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-790f-a909-26618fd02ca0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7ea3-917a-7bc5f6f77ab2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-790f-a909-26618fd02ca0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-76cc-9eaa-5e993e64eb5b" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7ea3-917a-7bc5f6f77ab2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-76cc-9eaa-5e993e64eb5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-7cb5-9d97-9f73305b80ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7ea3-917a-7bc5f6f77ab2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a0ee66-4996-7cb5-9d97-9f73305b80ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0ee66-4996-724e-9a32-868dd90da1f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a0ee66-4996-7ea3-917a-7bc5f6f77ab2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a0ee66-4996-724e-9a32-868dd90da1f1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a0ee66-4996-79a1-91cc-2a6e05b51c34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofValuationAssumptionsDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#StockBasedCompensationScheduleofValuationAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/StockBasedCompensationScheduleofValuationAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-772c-81cf-6917378574d6" 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_01a0ee66-4996-77d9-8582-4ec224243e73" 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_01a0ee66-4996-772c-81cf-6917378574d6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a0ee66-4996-77d9-8582-4ec224243e73" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-79c2-ace7-7ea9c7edf390" 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_01a0ee66-4996-77d9-8582-4ec224243e73" xlink:to="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-79c2-ace7-7ea9c7edf390" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79c2-ace7-7ea9c7edf390_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_01a0ee66-4996-79c2-ace7-7ea9c7edf390" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79c2-ace7-7ea9c7edf390_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-75e4-ab19-f1bf5cdc2fec" 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_01a0ee66-4996-79c2-ace7-7ea9c7edf390" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-75e4-ab19-f1bf5cdc2fec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7d67-b1ad-6be490fdab14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-75e4-ab19-f1bf5cdc2fec" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7d67-b1ad-6be490fdab14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_01a0ee66-4996-770e-b31a-4f95c432707a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-75e4-ab19-f1bf5cdc2fec" xlink:to="loc_us-gaap_WarrantMember_01a0ee66-4996-770e-b31a-4f95c432707a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_OverallotmentWarrantsMember_01a0ee66-4996-742c-a405-12734cdc2d18" xlink:href="bow-20260930.xsd#bow_OverallotmentWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WarrantMember_01a0ee66-4996-770e-b31a-4f95c432707a" xlink:to="loc_bow_OverallotmentWarrantsMember_01a0ee66-4996-742c-a405-12734cdc2d18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_01a0ee66-4996-7c6f-aaab-71d4c645e18b" 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_01a0ee66-4996-772c-81cf-6917378574d6" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_01a0ee66-4996-7c6f-aaab-71d4c645e18b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_01a0ee66-4996-773c-b4d8-d20ef9552d4f" 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_01a0ee66-4996-772c-81cf-6917378574d6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_01a0ee66-4996-773c-b4d8-d20ef9552d4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_01a0ee66-4996-7d8d-a83a-3e411500657f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a0ee66-4996-772c-81cf-6917378574d6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_01a0ee66-4996-7d8d-a83a-3e411500657f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_01a0ee66-4996-776c-9933-46c5e22e7f40" 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_01a0ee66-4996-772c-81cf-6917378574d6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_01a0ee66-4996-776c-9933-46c5e22e7f40" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/EarningsPerShareDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#EarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/EarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a0ee66-4996-7bbe-8836-a9b6dd311a71" 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_01a0ee66-4996-77bc-8427-bfc7aedc4a37" 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_01a0ee66-4996-7bbe-8836-a9b6dd311a71" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_01a0ee66-4996-77bc-8427-bfc7aedc4a37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-7d4c-b1c1-af4663d60c88" 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_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_01a0ee66-4996-77bc-8427-bfc7aedc4a37" xlink:to="loc_us-gaap_AwardTypeAxis_01a0ee66-4996-7d4c-b1c1-af4663d60c88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7d4c-b1c1-af4663d60c88_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_01a0ee66-4996-7d4c-b1c1-af4663d60c88" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-7d4c-b1c1-af4663d60c88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79be-8841-bac46bfdf900" 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_01a0ee66-4996-7d4c-b1c1-af4663d60c88" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79be-8841-bac46bfdf900" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0ee66-4996-7416-8bc4-30ac9dad6199" 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_01a0ee66-4996-79be-8841-bac46bfdf900" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a0ee66-4996-7416-8bc4-30ac9dad6199" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7ae4-aa82-14ca8530cb5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79be-8841-bac46bfdf900" xlink:to="loc_us-gaap_PerformanceSharesMember_01a0ee66-4996-7ae4-aa82-14ca8530cb5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_01a0ee66-4996-7575-b47f-06f9e5e496f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a0ee66-4996-79be-8841-bac46bfdf900" xlink:to="loc_us-gaap_WarrantMember_01a0ee66-4996-7575-b47f-06f9e5e496f4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_01a0ee66-4996-7187-b86e-dd269698705f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a0ee66-4996-7bbe-8836-a9b6dd311a71" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_01a0ee66-4996-7187-b86e-dd269698705f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_01a0ee66-4996-7ee9-b55f-89341bbace60" 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_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_01a0ee66-4996-7187-b86e-dd269698705f" xlink:to="loc_us-gaap_NetIncomeLoss_01a0ee66-4996-7ee9-b55f-89341bbace60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_01a0ee66-4996-7fbe-b6b5-da8421a15469" 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_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a0ee66-4996-7bbe-8836-a9b6dd311a71" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_01a0ee66-4996-7fbe-b6b5-da8421a15469" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_01a0ee66-4996-7d3d-9770-d1575d6d125a" 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_01a0ee66-4996-7fbe-b6b5-da8421a15469" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_01a0ee66-4996-7d3d-9770-d1575d6d125a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DilutiveSecuritiesAbstract_01a0ee66-4996-73f4-bfba-f7a06d504859" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DilutiveSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_01a0ee66-4996-7fbe-b6b5-da8421a15469" xlink:to="loc_us-gaap_DilutiveSecuritiesAbstract_01a0ee66-4996-73f4-bfba-f7a06d504859" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_01a0ee66-4996-72c5-b0c9-883c612e9e68" 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_DilutiveSecuritiesAbstract_01a0ee66-4996-73f4-bfba-f7a06d504859" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_01a0ee66-4996-72c5-b0c9-883c612e9e68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_01a0ee66-4996-7fc2-87a8-f48286acd6ba" 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_01a0ee66-4996-7fbe-b6b5-da8421a15469" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_01a0ee66-4996-7fc2-87a8-f48286acd6ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_EarningsPerShareBasicAndDilutedEPSAbstract_01a0ee66-4996-7de9-a5f4-a34f21d9c708" xlink:href="bow-20260930.xsd#bow_EarningsPerShareBasicAndDilutedEPSAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a0ee66-4996-7bbe-8836-a9b6dd311a71" xlink:to="loc_bow_EarningsPerShareBasicAndDilutedEPSAbstract_01a0ee66-4996-7de9-a5f4-a34f21d9c708" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_01a0ee66-4996-7a69-9aa0-f497276b64a0" 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_bow_EarningsPerShareBasicAndDilutedEPSAbstract_01a0ee66-4996-7de9-a5f4-a34f21d9c708" xlink:to="loc_us-gaap_EarningsPerShareBasic_01a0ee66-4996-7a69-9aa0-f497276b64a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_01a0ee66-4996-7c11-8a90-2cee790fab40" 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_bow_EarningsPerShareBasicAndDilutedEPSAbstract_01a0ee66-4996-7de9-a5f4-a34f21d9c708" xlink:to="loc_us-gaap_EarningsPerShareDiluted_01a0ee66-4996-7c11-8a90-2cee790fab40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_01a0ee66-4996-7201-9e31-e741ac7afceb" 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_01a0ee66-4996-7bbe-8836-a9b6dd311a71" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_01a0ee66-4996-7201-9e31-e741ac7afceb" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/RelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4996-7762-bb65-ff36da3e1a55" 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_01a0ee66-4996-71c6-a97c-3aebf274d33d" 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_01a0ee66-4996-7762-bb65-ff36da3e1a55" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a0ee66-4996-71c6-a97c-3aebf274d33d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_01a0ee66-4996-7238-ac1a-b9fb79ffcf12" 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_01a0ee66-4996-71c6-a97c-3aebf274d33d" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_01a0ee66-4996-7238-ac1a-b9fb79ffcf12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4996-7238-ac1a-b9fb79ffcf12_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_01a0ee66-4996-7238-ac1a-b9fb79ffcf12" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4996-7238-ac1a-b9fb79ffcf12_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4996-7e64-906e-fee2eaab17a2" 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_01a0ee66-4996-7238-ac1a-b9fb79ffcf12" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4996-7e64-906e-fee2eaab17a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AmFamMember_01a0ee66-4996-7416-8cb5-3c17b6c87327" xlink:href="bow-20260930.xsd#bow_AmFamMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_01a0ee66-4996-7e64-906e-fee2eaab17a2" xlink:to="loc_bow_AmFamMember_01a0ee66-4996-7416-8cb5-3c17b6c87327" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a0ee66-4996-7237-bcb2-e2931c8423dd" 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_01a0ee66-4996-71c6-a97c-3aebf274d33d" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a0ee66-4996-7237-bcb2-e2931c8423dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7237-bcb2-e2931c8423dd_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_01a0ee66-4996-7237-bcb2-e2931c8423dd" xlink:to="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7237-bcb2-e2931c8423dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7f21-8670-0f8eec216bae" 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_01a0ee66-4996-7237-bcb2-e2931c8423dd" xlink:to="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7f21-8670-0f8eec216bae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_01a0ee66-4996-7ad3-946a-8ab09f06f179" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_01a0ee66-4996-7f21-8670-0f8eec216bae" xlink:to="loc_us-gaap_RelatedPartyMember_01a0ee66-4996-7ad3-946a-8ab09f06f179" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_01a0ee66-4996-7612-a1e9-67b0eba15f37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a0ee66-4996-71c6-a97c-3aebf274d33d" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_01a0ee66-4996-7612-a1e9-67b0eba15f37" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_01a0ee66-4996-7612-a1e9-67b0eba15f37_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_01a0ee66-4996-7612-a1e9-67b0eba15f37" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_01a0ee66-4996-7612-a1e9-67b0eba15f37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_01a0ee66-4996-7e4e-bc44-ec99bc03c711" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_01a0ee66-4996-7612-a1e9-67b0eba15f37" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_01a0ee66-4996-7e4e-bc44-ec99bc03c711" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CedingFeesMember_01a0ee66-4996-719a-806b-1d6825e795b8" xlink:href="bow-20260930.xsd#bow_CedingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_01a0ee66-4996-7e4e-bc44-ec99bc03c711" xlink:to="loc_bow_CedingFeesMember_01a0ee66-4996-719a-806b-1d6825e795b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_01a0ee66-4996-7cbd-b1fb-9fdc285c8346" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a0ee66-4996-71c6-a97c-3aebf274d33d" xlink:to="loc_srt_CounterpartyNameAxis_01a0ee66-4996-7cbd-b1fb-9fdc285c8346" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_01a0ee66-4996-7cbd-b1fb-9fdc285c8346_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_01a0ee66-4996-7cbd-b1fb-9fdc285c8346" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_01a0ee66-4996-7cbd-b1fb-9fdc285c8346_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_01a0ee66-4996-77dc-9c30-f48b390d861f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_01a0ee66-4996-7cbd-b1fb-9fdc285c8346" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_01a0ee66-4996-77dc-9c30-f48b390d861f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AmFamMember_01a0ee66-4996-74c7-83fc-c42f07febfe7" xlink:href="bow-20260930.xsd#bow_AmFamMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_01a0ee66-4996-77dc-9c30-f48b390d861f" xlink:to="loc_bow_AmFamMember_01a0ee66-4996-74c7-83fc-c42f07febfe7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_BoldPenguinMember_01a0ee66-4996-7a25-9a0e-a1c449d8879b" xlink:href="bow-20260930.xsd#bow_BoldPenguinMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_01a0ee66-4996-77dc-9c30-f48b390d861f" xlink:to="loc_bow_BoldPenguinMember_01a0ee66-4996-7a25-9a0e-a1c449d8879b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_QuotaShareAgreementPercentage_01a0ee66-4996-759f-b47e-ebb5d43fbd96" xlink:href="bow-20260930.xsd#bow_QuotaShareAgreementPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4996-7762-bb65-ff36da3e1a55" xlink:to="loc_bow_QuotaShareAgreementPercentage_01a0ee66-4996-759f-b47e-ebb5d43fbd96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_01a0ee66-4996-7873-aa45-4ae208718b1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAmountsOfTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4996-7762-bb65-ff36da3e1a55" xlink:to="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_01a0ee66-4996-7873-aa45-4ae208718b1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededPremiumsWritten_01a0ee66-4996-79ea-89ca-39b07bede3b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededPremiumsWritten"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4996-7762-bb65-ff36da3e1a55" xlink:to="loc_us-gaap_CededPremiumsWritten_01a0ee66-4996-79ea-89ca-39b07bede3b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsWrittenNet_01a0ee66-4996-70af-b085-7008c6ba99d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsWrittenNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a0ee66-4996-7762-bb65-ff36da3e1a55" xlink:to="loc_us-gaap_PremiumsWrittenNet_01a0ee66-4996-70af-b085-7008c6ba99d1" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/CommitmentsandContingenciesSchedulesofGrossWrittenPremiumConcentrationofRiskDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#CommitmentsandContingenciesSchedulesofGrossWrittenPremiumConcentrationofRiskDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/CommitmentsandContingenciesSchedulesofGrossWrittenPremiumConcentrationofRiskDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_01a0ee66-4a25-7a6e-b597-29eff9ded95a" 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_01a0ee66-4a24-738f-905b-3b733b18e219" 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_01a0ee66-4a25-7a6e-b597-29eff9ded95a" xlink:to="loc_us-gaap_ConcentrationRiskTable_01a0ee66-4a24-738f-905b-3b733b18e219" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a24-79f2-8ac5-08b19cc1263d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_01a0ee66-4a24-738f-905b-3b733b18e219" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a24-79f2-8ac5-08b19cc1263d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a24-79f2-8ac5-08b19cc1263d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a24-79f2-8ac5-08b19cc1263d" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a24-79f2-8ac5-08b19cc1263d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a24-75a7-b614-e7fdc13364eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a24-79f2-8ac5-08b19cc1263d" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a24-75a7-b614-e7fdc13364eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_PremiumsWrittenGrossMember_01a0ee66-4a24-7d80-98be-223b515814ad" xlink:href="bow-20260930.xsd#bow_PremiumsWrittenGrossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a24-75a7-b614-e7fdc13364eb" xlink:to="loc_bow_PremiumsWrittenGrossMember_01a0ee66-4a24-7d80-98be-223b515814ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a24-77f4-a7a6-d635143a7d19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_01a0ee66-4a24-738f-905b-3b733b18e219" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a24-77f4-a7a6-d635143a7d19" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a24-77f4-a7a6-d635143a7d19_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a24-77f4-a7a6-d635143a7d19" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a24-77f4-a7a6-d635143a7d19_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a24-7573-8360-d549c727b7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a24-77f4-a7a6-d635143a7d19" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a24-7573-8360-d549c727b7b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_01a0ee66-4a24-7815-815f-2e237d07d56a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a24-7573-8360-d549c727b7b8" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_01a0ee66-4a24-7815-815f-2e237d07d56a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_01a0ee66-4a24-755f-869a-8780fafcb6b4" 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_ConcentrationRiskTable_01a0ee66-4a24-738f-905b-3b733b18e219" xlink:to="loc_srt_MajorCustomersAxis_01a0ee66-4a24-755f-869a-8780fafcb6b4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a24-755f-869a-8780fafcb6b4_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_01a0ee66-4a24-755f-869a-8780fafcb6b4" xlink:to="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a24-755f-869a-8780fafcb6b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a25-78bb-bfa8-ef90d54716f5" 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_01a0ee66-4a24-755f-869a-8780fafcb6b4" xlink:to="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a25-78bb-bfa8-ef90d54716f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_AmWINSGroupInc.BrokerMember_01a0ee66-4a25-776a-8b63-63ce698acf80" xlink:href="bow-20260930.xsd#bow_AmWINSGroupInc.BrokerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a25-78bb-bfa8-ef90d54716f5" xlink:to="loc_bow_AmWINSGroupInc.BrokerMember_01a0ee66-4a25-776a-8b63-63ce698acf80" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_RyanSpecialtyGroupHoldingsInc.BrokerMember_01a0ee66-4a25-7c5d-add3-c8694db9556c" xlink:href="bow-20260930.xsd#bow_RyanSpecialtyGroupHoldingsInc.BrokerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a25-78bb-bfa8-ef90d54716f5" xlink:to="loc_bow_RyanSpecialtyGroupHoldingsInc.BrokerMember_01a0ee66-4a25-7c5d-add3-c8694db9556c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CRCInsuranceServicesInc.BrokerMember_01a0ee66-4a25-766b-ad77-3c317ccdb349" xlink:href="bow-20260930.xsd#bow_CRCInsuranceServicesInc.BrokerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a25-78bb-bfa8-ef90d54716f5" xlink:to="loc_bow_CRCInsuranceServicesInc.BrokerMember_01a0ee66-4a25-766b-ad77-3c317ccdb349" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_MarshMcLennanCompaniesBrokerMember_01a0ee66-4a25-71e6-bb21-9a38badfda7c" xlink:href="bow-20260930.xsd#bow_MarshMcLennanCompaniesBrokerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_01a0ee66-4a25-78bb-bfa8-ef90d54716f5" xlink:to="loc_bow_MarshMcLennanCompaniesBrokerMember_01a0ee66-4a25-71e6-bb21-9a38badfda7c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_01a0ee66-4a25-7077-b8eb-5e4f36be7928" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_01a0ee66-4a25-7a6e-b597-29eff9ded95a" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_01a0ee66-4a25-7077-b8eb-5e4f36be7928" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" 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_01a0ee66-4a25-792b-8ef4-1275781b6b72" 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_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_LossContingenciesTable_01a0ee66-4a25-792b-8ef4-1275781b6b72" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestAxis_01a0ee66-4a25-7d1c-acc4-6b204d6bdf97" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0ee66-4a25-792b-8ef4-1275781b6b72" xlink:to="loc_srt_CreditRatingAMBestAxis_01a0ee66-4a25-7d1c-acc4-6b204d6bdf97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestDomain_01a0ee66-4a25-7d1c-acc4-6b204d6bdf97_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CreditRatingAMBestAxis_01a0ee66-4a25-7d1c-acc4-6b204d6bdf97" xlink:to="loc_srt_CreditRatingAMBestDomain_01a0ee66-4a25-7d1c-acc4-6b204d6bdf97_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestDomain_01a0ee66-4a25-7016-be96-9a26b3b8c449" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CreditRatingAMBestAxis_01a0ee66-4a25-7d1c-acc4-6b204d6bdf97" xlink:to="loc_srt_CreditRatingAMBestDomain_01a0ee66-4a25-7016-be96-9a26b3b8c449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AMBestARatingMember_01a0ee66-4a25-7399-b193-ede7dc7860c4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AMBestARatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CreditRatingAMBestDomain_01a0ee66-4a25-7016-be96-9a26b3b8c449" xlink:to="loc_srt_AMBestARatingMember_01a0ee66-4a25-7399-b193-ede7dc7860c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a25-7c99-8430-e9cf85fa69b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0ee66-4a25-792b-8ef4-1275781b6b72" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a25-7c99-8430-e9cf85fa69b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a25-7c99-8430-e9cf85fa69b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a25-7c99-8430-e9cf85fa69b4" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a25-7c99-8430-e9cf85fa69b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a25-7fea-a2c9-41f077df0a16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a0ee66-4a25-7c99-8430-e9cf85fa69b4" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a25-7fea-a2c9-41f077df0a16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverableMember_01a0ee66-4a25-7106-90a0-ad3a2a05d24e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a0ee66-4a25-7fea-a2c9-41f077df0a16" xlink:to="loc_us-gaap_ReinsuranceRecoverableMember_01a0ee66-4a25-7106-90a0-ad3a2a05d24e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a25-70fc-b72f-f9189ee7fcc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0ee66-4a25-792b-8ef4-1275781b6b72" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a25-70fc-b72f-f9189ee7fcc2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a25-70fc-b72f-f9189ee7fcc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a25-70fc-b72f-f9189ee7fcc2" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a25-70fc-b72f-f9189ee7fcc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a25-7955-9aa0-82ea70a1335a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a0ee66-4a25-70fc-b72f-f9189ee7fcc2" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a25-7955-9aa0-82ea70a1335a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsurerConcentrationRiskMember_01a0ee66-4a25-77c4-8300-a54c6fc39a7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsurerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_01a0ee66-4a25-7955-9aa0-82ea70a1335a" xlink:to="loc_us-gaap_ReinsurerConcentrationRiskMember_01a0ee66-4a25-77c4-8300-a54c6fc39a7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4a25-7423-9aa3-76b177129b9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_01a0ee66-4a25-792b-8ef4-1275781b6b72" xlink:to="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4a25-7423-9aa3-76b177129b9b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7423-9aa3-76b177129b9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskReinsurerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4a25-7423-9aa3-76b177129b9b" xlink:to="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7423-9aa3-76b177129b9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7539-a850-2db886b7e118" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskReinsurerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CededCreditRiskAxis_01a0ee66-4a25-7423-9aa3-76b177129b9b" xlink:to="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7539-a850-2db886b7e118" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ReinsurerOneMember_01a0ee66-4a25-76d0-9237-771853dace1d" xlink:href="bow-20260930.xsd#bow_ReinsurerOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7539-a850-2db886b7e118" xlink:to="loc_bow_ReinsurerOneMember_01a0ee66-4a25-76d0-9237-771853dace1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ReinsurerTwoMember_01a0ee66-4a25-7fe9-ad47-eb31dfa3a6e2" xlink:href="bow-20260930.xsd#bow_ReinsurerTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7539-a850-2db886b7e118" xlink:to="loc_bow_ReinsurerTwoMember_01a0ee66-4a25-7fe9-ad47-eb31dfa3a6e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ReinsurerThreeMember_01a0ee66-4a25-7a2b-9de9-21426d6f0c1e" xlink:href="bow-20260930.xsd#bow_ReinsurerThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskReinsurerDomain_01a0ee66-4a25-7539-a850-2db886b7e118" xlink:to="loc_bow_ReinsurerThreeMember_01a0ee66-4a25-7a2b-9de9-21426d6f0c1e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_01a0ee66-4a25-75ab-bbb9-541863fdb89b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_01a0ee66-4a25-75ab-bbb9-541863fdb89b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverablesAllowance_01a0ee66-4a25-7ed5-bebb-90fd306a8ac1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverablesAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_ReinsuranceRecoverablesAllowance_01a0ee66-4a25-7ed5-bebb-90fd306a8ac1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_01a0ee66-4a25-7df5-a77f-03856d88d9e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_01a0ee66-4a25-7df5-a77f-03856d88d9e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_01a0ee66-4a25-7d63-a6dd-90372a8840da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_01a0ee66-4a25-7d63-a6dd-90372a8840da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInSecondYear_01a0ee66-4a25-7e4e-9568-b49b9c450b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInSecondYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_PurchaseObligationDueInSecondYear_01a0ee66-4a25-7e4e-9568-b49b9c450b3a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInThirdYear_01a0ee66-4a25-739b-889a-1cffa64ff5e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInThirdYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_PurchaseObligationDueInThirdYear_01a0ee66-4a25-739b-889a-1cffa64ff5e3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued_01a0ee66-4a25-778a-bfc4-488172d5ba14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_01a0ee66-4a25-741c-acf5-d56169338d03" xlink:to="loc_us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued_01a0ee66-4a25-778a-bfc4-488172d5ba14" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://bowheadspecialty.com/role/SegmentGeographicandProductLineInformationScheduleofRevenuesbyUnderwritingDivisionDetails" xlink:type="simple" xlink:href="bow-20260930.xsd#SegmentGeographicandProductLineInformationScheduleofRevenuesbyUnderwritingDivisionDetails"/>
  <link:definitionLink xlink:role="http://bowheadspecialty.com/role/SegmentGeographicandProductLineInformationScheduleofRevenuesbyUnderwritingDivisionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_01a0ee66-4a25-765d-ac96-8be03166c2d6" 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_01a0ee66-4a25-7689-bc19-f4b0e5122412" 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_01a0ee66-4a25-765d-ac96-8be03166c2d6" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_01a0ee66-4a25-7689-bc19-f4b0e5122412" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a0ee66-4a25-7858-b60e-2deb46a6fb51" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_01a0ee66-4a25-7689-bc19-f4b0e5122412" xlink:to="loc_srt_ConsolidationItemsAxis_01a0ee66-4a25-7858-b60e-2deb46a6fb51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0ee66-4a25-7858-b60e-2deb46a6fb51_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a0ee66-4a25-7858-b60e-2deb46a6fb51" xlink:to="loc_srt_ConsolidationItemsDomain_01a0ee66-4a25-7858-b60e-2deb46a6fb51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a0ee66-4a25-7d50-89f5-7a186eda16d8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a0ee66-4a25-7858-b60e-2deb46a6fb51" xlink:to="loc_srt_ConsolidationItemsDomain_01a0ee66-4a25-7d50-89f5-7a186eda16d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a0ee66-4a25-7304-a6ef-27297d4fff77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a0ee66-4a25-7d50-89f5-7a186eda16d8" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a0ee66-4a25-7304-a6ef-27297d4fff77" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a0ee66-4a25-770c-bfcf-fccf301372b1" 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_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_01a0ee66-4a25-7689-bc19-f4b0e5122412" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a0ee66-4a25-770c-bfcf-fccf301372b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0ee66-4a25-770c-bfcf-fccf301372b1_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_01a0ee66-4a25-770c-bfcf-fccf301372b1" xlink:to="loc_us-gaap_SegmentDomain_01a0ee66-4a25-770c-bfcf-fccf301372b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a0ee66-4a25-7cab-b0ae-de057b8444a3" 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_01a0ee66-4a25-770c-bfcf-fccf301372b1" xlink:to="loc_us-gaap_SegmentDomain_01a0ee66-4a25-7cab-b0ae-de057b8444a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_UnderwritingDivisionMember_01a0ee66-4a25-7bdd-8e32-709d0342a5d9" xlink:href="bow-20260930.xsd#bow_UnderwritingDivisionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a0ee66-4a25-7cab-b0ae-de057b8444a3" xlink:to="loc_bow_UnderwritingDivisionMember_01a0ee66-4a25-7bdd-8e32-709d0342a5d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsAxis_01a0ee66-4a25-768b-95af-58dd8fbf324a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_01a0ee66-4a25-7689-bc19-f4b0e5122412" xlink:to="loc_us-gaap_SubsegmentsAxis_01a0ee66-4a25-768b-95af-58dd8fbf324a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-768b-95af-58dd8fbf324a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsegmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsegmentsAxis_01a0ee66-4a25-768b-95af-58dd8fbf324a" xlink:to="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-768b-95af-58dd8fbf324a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-7e1b-a1c7-77aa588b7079" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsegmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsegmentsAxis_01a0ee66-4a25-768b-95af-58dd8fbf324a" xlink:to="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-7e1b-a1c7-77aa588b7079" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_CasualtyMember_01a0ee66-4a25-764f-85d7-a22be1a73fcd" xlink:href="bow-20260930.xsd#bow_CasualtyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-7e1b-a1c7-77aa588b7079" xlink:to="loc_bow_CasualtyMember_01a0ee66-4a25-764f-85d7-a22be1a73fcd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_ProfessionalLiabilityMember_01a0ee66-4a25-79fc-a224-59d80e0a640b" xlink:href="bow-20260930.xsd#bow_ProfessionalLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-7e1b-a1c7-77aa588b7079" xlink:to="loc_bow_ProfessionalLiabilityMember_01a0ee66-4a25-79fc-a224-59d80e0a640b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_HealthcareLiabilityMember_01a0ee66-4a25-74f6-8f1e-e72dac55845a" xlink:href="bow-20260930.xsd#bow_HealthcareLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-7e1b-a1c7-77aa588b7079" xlink:to="loc_bow_HealthcareLiabilityMember_01a0ee66-4a25-74f6-8f1e-e72dac55845a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bow_BaleenSpecialtyMember_01a0ee66-4a25-7ba4-84aa-d468f29915f1" xlink:href="bow-20260930.xsd#bow_BaleenSpecialtyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsegmentsDomain_01a0ee66-4a25-7e1b-a1c7-77aa588b7079" xlink:to="loc_bow_BaleenSpecialtyMember_01a0ee66-4a25-7ba4-84aa-d468f29915f1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsWrittenNet_01a0ee66-4a25-74a5-b09c-5bac390cd667" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsWrittenNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_01a0ee66-4a25-765d-ac96-8be03166c2d6" xlink:to="loc_us-gaap_PremiumsWrittenNet_01a0ee66-4a25-74a5-b09c-5bac390cd667" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
