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

    <schemaVersion>X0607</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2026-03-18</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001943421</issuerCik>
        <issuerName>Rubico Inc.</issuerName>
        <issuerTradingSymbol>RUBI</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002125818</rptOwnerCik>
            <rptOwnerName>Daskalakis Georgios</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>true</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>AIGIALEIAS 48, 4TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MAROUSSI</rptOwnerCity>
            <rptOwnerNonUSStateTerritory></rptOwnerNonUSStateTerritory>
            <rptOwnerCountry>J3</rptOwnerCountry>
            <rptOwnerZipCode>15125</rptOwnerZipCode>
            <rptOwnerStateDescription>GREECE</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>/s/ Georgios Daskalakis</signatureName>
        <signatureDate>2026-04-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
