Filed Pursuant to Rule 433

Registration No. 333-271922

August 7, 2025

Supplementing the Preliminary

Prospectus Supplement dated August 7, 2025

(To Prospectus dated May 15, 2023)

MPLX LP

Pricing Term Sheet

August 7, 2025

$1,250,000,000 4.800% Senior Notes due 2031

$750,000,000 5.000% Senior Notes due 2033

$1,500,000,000 5.400% Senior Notes due 2035

$1,000,000,000 6.200% Senior Notes due 2055

Issuer:	MPLX LP
Expected Ratings (Moody’s / S&P / Fitch)*:	Baa2/BBB/BBB
Net proceeds (after underwriting discounts but before expenses) to the Issuer:	$4,426,747,500.00
Trade Date:	August 7, 2025
Settlement Date**:	August 11, 2025 (T+2)
4.800% Senior Notes due 2031
Principal Amount:	$1,250,000,000
Maturity Date:	February 15, 2031
Coupon:	4.800%
Price to Public:	99.880% of the principal amount plus accrued interest, if any, from August 11, 2025
Yield to Maturity:	4.825%
Spread to Benchmark Treasury:	+103 bps
Benchmark Treasury:	3.875% due July 31, 2030
Benchmark Treasury Price / Yield:	100-11+ / 3.795%

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Interest Payment Dates:	February 15 and August 15, commencing February 15, 2026, to holders of record at the close of business on the preceding February 1 and August 1, respectively
Optional Redemption Provisions:
Make-Whole Call:	T+20 bps (at any time before January 15, 2031)
Par Call:	At any time on or after January 15, 2031
Special Mandatory Redemption:	Mandatorily redeemable at 101% of the principal plus accrued and unpaid interest under the circumstances described in the preliminary prospectus supplement for this offering.
CUSIP / ISIN:	55336VCA6 / US55336VCA61
5.000% Senior Notes due 2033
Principal Amount:	$750,000,000
Maturity Date:	January 15, 2033
Coupon:	5.000%
Price to Public:	98.936% of the principal amount plus accrued interest, if any, from August 11, 2025
Yield to Maturity:	5.175%
Spread to Benchmark Treasury:	+118 bps
Benchmark Treasury:	4.000% due July 31, 2032
Benchmark Treasury Price / Yield:	100-01 / 3.995%
Interest Payment Dates:	January 15 and July 15, commencing January 15, 2026, to holders of record at the close of business on the preceding January 1 and July 1, respectively
Optional Redemption Provisions:
Make-Whole Call:	T+20 bps (at any time before November 15, 2032)
Par Call:	At any time on or after November 15, 2032

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Special Mandatory Redemption:	Mandatorily redeemable at 101% of the principal plus accrued and unpaid interest under the circumstances described in the preliminary prospectus supplement for this offering.
CUSIP / ISIN:	55336VCB4 / US55336VCB45
5.400% Senior Notes due 2035
Principal Amount:	$1,500,000,000
Maturity Date:	September 15, 2035
Coupon:	5.400%
Price to Public:	98.943% of the principal amount plus accrued interest, if any, from August 11, 2025
Yield to Maturity:	5.537%
Spread to Benchmark Treasury:	+130 bps
Benchmark Treasury:	4.250% due May 15, 2035
Benchmark Treasury Price / Yield:	100-03 / 4.237%
Interest Payment Dates:	March 15 and September 15, commencing March 15, 2026, to holders of record at the close of business on the preceding March 1 and September 1, respectively
Optional Redemption Provisions:
Make-Whole Call:	T+20 bps (at any time before June 15, 2035)
Par Call:	At any time on or after June 15, 2035
CUSIP / ISIN:	55336VCC2 / US55336VCC28
6.200% Senior Notes due 2055
Principal Amount:	$1,000,000,000
Maturity Date:	September 15, 2055
Coupon:	6.200%

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Price to Public:	98.277% of the principal amount plus accrued interest, if any, from August 11, 2025
Yield to Maturity:	6.328%
Spread to Benchmark Treasury:	+150 bps
Benchmark Treasury:	4.625% due February 15, 2055
Benchmark Treasury Price / Yield:	96-26+ / 4.828%
Interest Payment Dates:	March 15 and September 15, commencing March 15, 2026, to holders of record at the close of business on the preceding March 1 and September 1, respectively
Optional Redemption Provisions:
Make-Whole Call:	T+25 bps (at any time before March 15, 2055)
Par Call:	At any time on or after March 15, 2055
CUSIP / ISIN:	55336VCD0 / US55336VCD01
Joint Book-Running Managers:	J.P. Morgan Securities LLC Goldman Sachs & Co. LLC BofA Securities, Inc. Mizuho Securities USA LLC TD Securities (USA) LLC Wells Fargo Securities, LLC Barclays Capital Inc. Citigroup Global Markets Inc. MUFG Securities Americas Inc. RBC Capital Markets, LLC

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Co-Managers: Scotia Capital (USA) Inc. SMBC Nikko Securities America, Inc. Truist Securities, Inc. U.S. Bancorp Investments, Inc. Fifth Third Securities, Inc. Huntington Securities, Inc. Morgan Stanley & Co. LLC PNC Capital Markets LLC Comerica Securities, Inc. Siebert Williams Shank & Co., LLC Academy Securities, Inc. BNY Mellon Capital Markets, LLC Cabrera Capital Markets LLC

* A securities rating is not a recommendation to buy, sell or hold securities and may be subject to revision or withdrawal at any time.

The issuer has filed a registration statement (including a prospectus) and a prospectus supplement with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement, the prospectus supplement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling J.P. Morgan Securities LLC collect at 1-212-834-4533, Goldman Sachs & Co. LLC toll-free at 1-866-471-2526, BofA Securities, Inc. toll-free at 1-800-294-1322, Mizuho Securities USA LLC telephone: (toll-free) 866-271-7403, TD Securities (USA) LLC telephone (toll-free): 855-495-9846 or Wells Fargo Securities, LLC telephone (toll-free): 1-800-645-3751.

** It is expected that delivery of the notes will be made against payment therefor on or about August 11, 2025, which is the second business day following the date hereof (such settlement cycle being referred to as “T+2”). Under Rule 15c6-1 under the Exchange Act, trades in the secondary market generally are required to settle in one business day unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes prior to the date that is more than one business day preceding the settlement date will be required, by virtue of the fact that the notes initially will settle in T+2, to specify an alternative settlement cycle at the time of any such trade to prevent a failed settlement. Purchasers of the notes who wish to trade the notes prior to their date of delivery hereunder should consult their own advisors.

Any legends, disclaimers or other notices that may appear below are not applicable to this communication and should be disregarded. Such legends, disclaimers or other notices have been automatically generated as a result of this communication having been sent via Bloomberg or another system.

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