March 30, 2020

Michael J. Hennigan
President and Chief Executive Officer
MPLX LP
200 E. Hardin Street
Findlay, OH 45840

       Re: MPLX LP
           Registration Statement on Form S-4
           Filed March 20, 2020
           File No. 333-237317

Dear Mr. Hennigan:

       We have limited our review of your registration statement to those
issues we have
addressed in our comments. In some of our comments, we may ask you to provide
us with
information so we may better understand your disclosure.

       Please respond to this letter by amending your registration statement
and providing the
requested information. If you do not believe our comments apply to your facts
and
circumstances or do not believe an amendment is appropriate, please tell us why
in your
response.

       After reviewing any amendment to your registration statement and the
information you
provide in response to these comments, we may have additional comments.

Registration Statement on Form S-4

General

1.     We note that the forum selection provision in Section 16.9 of your Fifth
Amended and
       Restated Agreement of Limited Partnership identifies the Court of
Chancery of the State
       of Delaware as the exclusive forum for certain litigation, including
claims, suits, actions
       or proceedings "brought in a derivative manner on behalf of the
Partnership." Please
       disclose whether this provision applies to actions arising under the
Securities Act or
       Exchange Act. In that regard, we note that Section 27 of the Exchange
Act creates
       exclusive federal jurisdiction over all suits brought to enforce any
duty or liability created
       by the Exchange Act or the rules and regulations thereunder, and Section
22 of the
       Securities Act creates concurrent jurisdiction for federal and state
courts over all suits
       brought to enforce any duty or liability created by the Securities Act
or the rules and
 Michael J. Hennigan
MPLX LP
March 30, 2020
Page 2
         regulations thereunder. If the provision applies to Securities Act
claims, please also revise
         your prospectus to state that there is uncertainty as to whether a
court would enforce such
         provision and that investors cannot waive compliance with the federal
securities laws and
         the rules and regulations thereunder. If this provision does not apply
to actions arising
         under the Securities Act or Exchange Act, please tell us how you will
inform investors in
         future filings that the provision does not apply to any actions
arising under the Securities
         Act or Exchange Act.
        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration
statement.

      Please contact Karina Dorin, Staff Attorney, at (202) 551-3763 or Lauren
Nguyen, Legal
Branch Chief, at (202) 551-3642 with any questions.



FirstName LastNameMichael J. Hennigan                          Sincerely,
Comapany NameMPLX LP
                                                               Division of
Corporation Finance
March 30, 2020 Page 2                                          Office of Energy
& Transportation
FirstName LastName