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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2005-04-04</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000003673</issuerCik>
        <issuerName>ALLEGHENY ENERGY, INC</issuerName>
        <issuerTradingSymbol>AYE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001322841</rptOwnerCik>
            <rptOwnerName>Park Hyun</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ALLEGHENY ENERGY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>800 CABIN HILL DRIVE</rptOwnerStreet2>
            <rptOwnerCity>GREENSBURG</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>15601</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice Pres. &amp; General Counsel</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>Hyun Park</signatureName>
        <signatureDate>2005-04-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
