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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - Q ( Mark One ) ☑ ☐ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended March 31 , 2021 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Commission file number 1-1513 to W Marathon Oil® Marathon Oil Corporation Delaware ( Exact name of registrant as specified in its charter ) ( State or other jurisdiction of incorporation or organization ) Title of each class Common Stock , par value $ 1.00 5555 San Felipe Street , Houston , Texas 77056-2723 ( Address of principal executive offices ) ( 713 ) 629-6600 ( Registrant's telephone number , including area code ) 25-0996816 ( I.R.S. Employer Identification No. ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol MRO Name of each exchange on which registered New York Stock Exchange 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 þ No o 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 þ No o Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , 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 þ Smaller reporting company ☐ Accelerated filer O Non - accelerated filer o Emerging growth company 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 is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes □ No þ There were 788,153,032 shares of Marathon Oil Corporation common stock outstanding as of April 30 , 2021 .