|Traded as||NYSE: MRO
S&P 500 Component
|Predecessor||The Ohio Oil Company, U.S. Steel|
|Headquarters||Marathon Oil Tower
|Lee M. Tillman, President & CEO|
|438 thousand barrels of oil equivalent (2,680,000 GJ) per day |
|Revenue||US$ 5.522 billion (2015)|
|US$ -3.03 billion (2015)|
|US$ -2.204 billion (2015)|
|Total assets||US$ 32.311 billion (2015)|
|Total equity||US$ 18.553 billion (2015)|
Number of employees
As of December 31, 2015, the company had 2.163 billion barrels of oil equivalent (1.323×1010 GJ) of estimated proved reserves, of which 44% was in the United States, 32% was in Canada, 12% was in Equatorial Guinea, and 11% was in other countries in Africa, primarily Libya.
The company has concessions with the Waha Oil Company in Libya. Libya accounts for 235 million barrels of oil equivalent (1.44×109 GJ) of estimated proved reserves, although the company did not sell any product from these operations in 2015 since operations were interrupted by civil and political unrest. 
In 2016, the company plans to spend $1.4 billion on capital expenditures, of which $1.2 billion will be spent in North America, including $600 million in the Eagle Ford and $200 million in the Bakken formation.
Marathon began as The Ohio Oil Company in 1887. In 1889, it was purchased by John D. Rockefeller's Standard Oil. It remained a part of Standard Oil until Standard Oil was broken in 1911. In 1930, The Ohio Oil Company bought the Transcontinental Oil Company and established the "Marathon" brand name. In 1962, the company changed its name to "Marathon Oil Company".
In 1982, Mobil made a hostile offer to buy the company; however, the board of Marathon Oil rejected the offer and instead sold the company to United States Steel. A legal battle ensued thereafter. 
After the merger, the headquarters was moved to Houston, Texas in 1990 but the company's refining subsidiary maintained its headquarters in Findlay.
In late 2003, Marathon Oil and its partners Noble Energy and AMPCO started the Bioko Island Malaria Control Project (BIMCP) in Equatorial Guinea. Malaria control activities included indoor residual spraying, improved diagnosis and case management, and capacity building to contain future outbreaks. BIMCP had proven being successful in reducing malaria transmission, reducing the proportion of children with malaria parasites, and improving iron status. BIMCP is perceived as a model of hands-on corporate involvement in a humanitarian effort with government, non-profits and academic organizations to reduce the burden of malaria in countries located in Equatorial Africa.  The President of Equatorial Guinea, Obiang Nguema, is one of the world's worst dictators, according to Parade Magazine. Marathon's humanitarian efforts have mitigated some of the criticism resulting from its dealings with Nguema's regime. In 2008, Marathon Oil and Lestis Group started the Central Basin Control Project (CBCP)
In 2007, Marathon purchased for approximately $6.6 billion, Marathon acquired Western Oil Sands and gained ownership of its 20 percent stake in the Athabasca Oil Sands Project in northern Alberta and other assets in the midwestern United States. The Athabasca project's Muskeg River Mine was producing 155,000 barrels a day of bitumen at the time.
- Marathon Oil Corporation 2015 Form 10-K
- "Mobil Corp. v. Marathon Oil Co.: Tender Offeror's Right to Injunctive Relief Recognized". Pace Law Review. April 1983.
- SALPUKAS, AGIS (March 30, 1984). "MARATHON WILL BUY HUSKY UNIT". New York Times.
- Breed, Alan G. (May 16, 1997). "Ashland, Marathon Announce Alliance". Kentucky New Era.
- United States Steel Corporation Form S-4, September 7, 2001
- "Husky snaps up Marathon assets". Globe and Mail. August 21, 2003.
- "Marathon to Sell Interest in Yates Field to Kinder Morgan Energy Partners". PRNewswire. October 30, 2003.
- Bioko Island Malaria Control Project
- "More of the World's Worst Dictators". Parade Magazine. March 22, 2009.
- "Marathon to buy Western Oil Sands for $6.5B". CBC News. July 31, 2007. Retrieved 12 July 2017.
- "Marathon spin-off gives Ohio fifth largest refiner". Associated Press via Yahoo! Finance. June 30, 2011.
- China's Sinopec buys Marathon's Angola oil fields for $1.52 billion, Reuters, June 23, 2013
- Marathon Oil to sell stake in Angolan field for $590 million, Reuters, September 10, 2013
- Det norske acquires Marathon Oil Norge AS, June 2, 2014