Marathon Petroleum Corporation is an American petroleum refining, marketing, and transportation company headquartered in Findlay, Ohio. It was elected the best employer of United States in 2016 by Forbes. The company was a wholly owned subsidiary of Marathon Oil until a corporate spin-off in 2011.

The company owns:

Marathon Petroleum Corporation was formed on November 9, 2005 as a subsidiary of Marathon Oil.

Marathon Oil, the company's former parent, dates back to 1887 when several small oil companies in Ohio banded together to form The Ohio Oil Company. From 1982 until 2002, Marathon Oil was a subsidiary of U.S. Steel.

The predecessor company of Marathon Petroleum Corporation, Marathon Petroleum Company LLC, formerly known as Marathon Ashland Petroleum LLC, was formed by the merger of the refining operations of Marathon Oil and Ashland Inc. in 1998. In 2005, the company became a 100% owned subsidiary of Marathon Oil.

In 2006, Marathon began using STP-branded additives in its gasoline.

In 2009, the company completed a $3.9 billion expansion of its refinery in Garyville, Louisiana that increased the plant’s capacity by 180,000 barrels per day.

In 2010, the company sold its 74,000 barrel-per-day refinery in St. Paul Park, Minnesota along with associated terminals, pipelines, and inventory as well as 166 SuperAmerica convenience stores to Northern Tier Energy for $900 million.

On June 30, 2011, Marathon Oil distributed all of its shares in the company to its shareholders via a corporate spin-off.

In June 2012, Wheeling, West Virginia-based Tri-State Petroleum signed a contract to switch 50 stations in Ohio, Pennsylvania, and West Virginia to the Marathon brand. Most of Tri-State's stations before the deal were ExxonMobil-branded stations, the majority Exxon as well as a few scattered Mobil stations in the immediate Wheeling area. Included in the deal were 18 Exxon stations in the Pittsburgh metropolitan area, significantly boosting Marathon's presence in the Pittsburgh market, where former parent company U.S. Steel is based. (Exxon would offset its Pittsburgh losses by taking over the retail contracts of several Shell stations in the area, leaving Shell with a significantly reduced presence, while the Mobil brand was withdrawn from the Northern Panhandle of West Virginia altogether.) Before the deal, Marathon had a much smaller presence in Western Pennsylvania, while having a somewhat larger presence in West Virginia and an almost ubiquitous presence in Southern Ohio.

In 2013, Marathon purchased numerous assets from BP including a 451,000 barrel per day refinery in Texas City, Texas, four light product distribution terminals, and retail marketing contracts for 1,200 retail stations throughout the southeastern United States.

In 2014, Speedway LLC, a subsidiary of the company, purchased the retail operations of Hess Corporation for $2.82 billion.

In 2016, a fire at the Galveston Bay refinery in Texas City, Texas injured three contract workers, resulting in a lawsuit seeking $1 million in damages. Multiple lawsuits were filed resulting in Marathon paying $86 million to settle.