<SEC-DOCUMENT>0001209191-17-025444.txt : 20170405
<SEC-HEADER>0001209191-17-025444.hdr.sgml : 20170405
<ACCEPTANCE-DATETIME>20170405093605
ACCESSION NUMBER:		0001209191-17-025444
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170403
FILED AS OF DATE:		20170405
DATE AS OF CHANGE:		20170405

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MPLX LP
		CENTRAL INDEX KEY:			0001552000
		STANDARD INDUSTRIAL CLASSIFICATION:	PIPE LINES (NO NATURAL GAS) [4610]
		IRS NUMBER:				270005456
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		200 E. HARDIN STREET
		CITY:			FINDLAY
		STATE:			OH
		ZIP:			45840
		BUSINESS PHONE:		(419) 421-2159

	MAIL ADDRESS:	
		STREET 1:		200 E. HARDIN STREET
		CITY:			FINDLAY
		STATE:			OH
		ZIP:			45840

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Rosson Paula L
		CENTRAL INDEX KEY:			0001526751

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-35714
		FILM NUMBER:		17741279

	MAIL ADDRESS:	
		STREET 1:		1515 ARAPAHOE STREET
		STREET 2:		TOWER 1  SUITE 1600
		CITY:			DENVER
		STATE:			CO
		ZIP:			80202
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-04-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001552000</issuerCik>
        <issuerName>MPLX LP</issuerName>
        <issuerTradingSymbol>MPLX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001526751</rptOwnerCik>
            <rptOwnerName>Rosson Paula L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MPLX LP</rptOwnerStreet1>
            <rptOwnerStreet2>200 E. HARDIN STREET</rptOwnerStreet2>
            <rptOwnerCity>FINDLAY</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>45840</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Senior VP and CAO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units (Limited Partner Interests)</value>
            </securityTitle>
            <transactionDate>
                <value>2017-04-03</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6367</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45480</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <remarks>The Reporting Person is the Senior Vice President and Chief Accounting Officer of MPLX GP LLC, the general partner of the Issuer. The Issuer is managed by the directors and executive officers of MPLX GP LLC.</remarks>

    <ownerSignature>
        <signatureName>/s/ Molly R. Benson, Attorney-in-Fact for Paula L. Rosson</signatureName>
        <signatureDate>2017-04-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
