<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-07-29</periodOfReport>

    <issuer>
        <issuerCik>0002067129</issuerCik>
        <issuerName>Neptune Insurance Holdings Inc.</issuerName>
        <issuerTradingSymbol>NP</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001894163</rptOwnerCik>
            <rptOwnerName>FTV VII, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>601 CALIFORNIA STREET, FLOOR 19</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94108</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002087488</rptOwnerCik>
            <rptOwnerName>FTV NE-Aggregator, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>601 CALIFORNIA STREET, FLOOR 19</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94108</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002086942</rptOwnerCik>
            <rptOwnerName>Growth VII-Centre, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>601 CALIFORNIA STREET, FLOOR 19</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94108</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002087425</rptOwnerCik>
            <rptOwnerName>FTV Management VII, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>601 CALIFORNIA STREET, FLOOR 19</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94108</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-07-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1867840</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>33.22</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14442941</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">After giving effect to the sale reported in this statement, the shares of Class A Common Stock are directly held as follows: 12,685,340 by FTV VII, L.P. (&quot;FTV VII&quot;), 878,801 by FTV-NE Aggregator, LLC (&quot;FTV-NE Aggregator&quot;) and 878,800 by Growth VII-Centre, L.P. (&quot;Growth VII-Centre&quot;).</footnote>
        <footnote id="F2">FTV-NE Aggregator is managed by FTV VII, its sole member, which is managed by FTV Management VII, L.P. (&quot;FTV Management&quot;), its general partner. Growth VII-Centre is managed by FTV Management, its general partner.</footnote>
        <footnote id="F3">Each of the reporting persons disclaims beneficial ownership of the reported securities, except to the extent of such reporting person's pecuniary interest therein, if any. The filing of this statement shall not be deemed an admission by any reporting person of beneficial ownership of the reported securities.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>FTV VII, L.P., By: FTV Management VII, L.P., its General Partner, By: FTV VII GP, L.L.C., its General Partner, By: /s/ Andy Fleischman, Name: Andy Fleischman, Title: Managing Member</signatureName>
        <signatureDate>2026-07-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>FTV-NE Aggregator, LLC, By: /s/ Andy Fleischman, Name: Andy Fleischman, Title: Managing Member</signatureName>
        <signatureDate>2026-07-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Growth VII-Centre, L.P., By: FTV Management VII, L.P., its General Partner, By: FTV VII GP, L.L.C., its General Partner, By: /s/ Andy Fleischman, Name: Andy Fleischman, Title: Managing Member</signatureName>
        <signatureDate>2026-07-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>FTV Management VII, L.P., By: FTV VII GP, L.L.C., its General Partner, By: /s/ Andy Fleischman, Name: Andy Fleischman, Title: Managing Member</signatureName>
        <signatureDate>2026-07-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
