EXHIBIT 24

MPLX LP POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and
appoints Molly R. Benson, Jodi E. Baker, Peter I. Kern and Shane T. Pfleiderer
(the "Attorneys"), and each of them, as the true and lawful attorney or
attorneys-in-fact, with full power of substitution and revocation, for the
undersigned and in the name, place and stead of the undersigned, in any and all
capacities, to execute, on behalf of the undersigned, (1) any and all notices
pursuant to Rule 144 under the Securities Act of 1933 with respect to sales of
common units or other securities of MPLX LP, including, without limitation, all
notices of proposed sale on Form 144, and (2) any and all statements or reports
under Section 16 of the Securities Exchange Act of 1934 with respect to the
beneficial ownership of common units or other securities of MPLX LP, including,
without limitation, all initial statements of beneficial ownership on Form 3,
all statements of changes in beneficial ownership on Form 4, all annual
statements of beneficial ownership on Form 5 and all successor or similar forms,
to be filed with the Securities and Exchange Commission, to execute any and all
amendments or supplements to any such notices, statements or reports, and to
file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting to said
Attorney or Attorneys-in-fact, and each of them, full power and authority to do
so and perform each and every act and thing requisite and necessary to be done
in and about the premises (including, without limitation, completing, executing,
delivering and filing a Form ID to apply for electronic filing codes), as fully
and to all intents and purposes as the undersigned might or could do in person,
and hereby ratifying and confirming all that said Attorney or Attorneys-in-fact,
or any of them, or their substitute or substitutes, may lawfully do or cause to
be done by virtue hereof.  The undersigned acknowledges that the foregoing
Attorneys-in-fact, and each of them, in serving in such capacity at the request
of the undersigned, are not assuming any of the responsibilities of the
undersigned to comply with Section 16 of the Securities Exchange Act of 1934 or
any other legal requirement.  This Power of Attorney shall remain in effect
until revoked in writing by the undersigned.



____/s/ John S. Swearingen____
          John S. Swearingen

Date:  1/29/2016