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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2024-01-19</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001680048</issuerCik>
        <issuerName>MUSTANG BIO, INC.</issuerName>
        <issuerTradingSymbol>MBIO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001282721</rptOwnerCik>
            <rptOwnerName>MURPHY JAMES B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MUSTANG BIO, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>377 PLANTATION STREET</rptOwnerStreet2>
            <rptOwnerCity>WORCESTER</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01605</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Interim CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>/s/ James B. Murphy</signatureName>
        <signatureDate>2024-02-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
