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    <periodOfReport>2015-04-30</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001338613</issuerCik>
        <issuerName>Regency Energy Partners LP</issuerName>
        <issuerTradingSymbol>RGP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001240071</rptOwnerCik>
            <rptOwnerName>Bradley Michael J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2001 BRYAN STREET, SUITE 3700</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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    <footnotes>
        <footnote id="F1">Immediately prior to the merger of a wholly owned subsidiary of Energy Transfer Partners, L.P. (&quot;ETP&quot;) with and into Regency Energy Partners LP (&quot;RGP&quot;) effective on April 30, 2015 (the &quot;Merger&quot;), all of the reporting person's Phantom Units granted pursuant to the reporting person's November 22, 2010, December 17, 2010, December 21, 2011, December 17, 2012, January 3, 2014 and December 19, 2014 Phantom Unit awards vested in full, and an equal number of RGP common units were deemed issued in settlement thereof.</footnote>
        <footnote id="F2">Each Phantom Unit is the economic equivalent of one common unit representing a limited partner interest in RGP.</footnote>
        <footnote id="F3">Common Units withheld to cover taxes payable upon vesting of Phantom Units reported in Table II.</footnote>
        <footnote id="F4">Closing price for the Issuer's common units on April 28, 2015, the date used to calculate awards.</footnote>
        <footnote id="F5">Disposition in connection with the Merger. On April 29, 2015, the last trading day for the RGP common units, the closing price of the RGP common units was $23.47 per unit and the closing price of ETP's common units was $55.30 per unit. Each RGP common unit outstanding, and each common unit deemed issued and outstanding pursuant to the reported vestings was converted into the right to receive 0.4124 ETP common units.</footnote>
        <footnote id="F6">Not applicable.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ A. Troy Sturrock, as power of attorney</signatureName>
        <signatureDate>2015-05-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
