Marathon Oil Corporation was an independent American energy company focused on the exploration, production, and marketing of hydrocarbons, including oil and natural gas. Founded in 1887 as the Ohio Oil Company, it became known as Marathon Oil in 1962 and was headquartered in Houston, Texas. The company operated globally, with significant assets in the United States and international locations like Equatorial Guinea.

Marathon Oil's operations were divided into three main segments: Exploration & Production, Oil Sands Mining, and Integrated Gas. The company was involved in the exploration and production of liquid hydrocarbons and natural gas, primarily from U.S. shale plays. It also engaged in mining and upgrading bitumen from oil sands in Canada and produced natural gas-derived products, including liquefied natural gas and methanol. Marathon Oil had a strong legacy in the energy sector, with substantial proven reserves and a commitment to technological advancements throughout its history. In 2024, Marathon Oil was acquired by ConocoPhillips.