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( Mark One ) UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 Form 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 or TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number 1-16335 Magellan Midstream Partners , L.P. ( Exact name of registrant as specified in its charter ) Delaware ( State or other jurisdiction of incorporation or organization ) Title of Each Class Common Units One Williams Center , P.O. Box 22186 , Tulsa , Oklahoma 74121-2186 ( Address of principal executive offices and zip code ) ( 918 ) 574-7000 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : 73-1599053 ( I.R.S. Employer Identification No. ) Trading Symbol ( s ) Name of Each Exchange on Which Registered New York Stock Exchange MMP Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes Indicate by check mark whether the registrant : ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes No o No o No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No o Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company or an emerging growth company . See the definitions of “ large accelerated filer , ” “ accelerated filer , ” “ smaller reporting company ” and “ emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer > Accelerated filer o Non - accelerated filer o Smaller reporting company Emerging growth company 0 If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . O Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No X The aggregate market value of the registrant's voting and non - voting common units held by non - affiliates computed by reference to the price at which the common units were last sold as of June 30 , 2020 was $ 9,686,843,947 . As of February 17 , 2021 , there were 223,282,818 common units outstanding . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's Proxy Statement prepared for the solicitation of proxies in connection with the 2021 Annual Meeting of Limited Partners are to be incorporated by reference in Part III of this Form 10 - K .