Sinclair Oil Corporation was an American petroleum corporation founded by Harry F. Sinclair on May 1, 1916. The Sinclair Oil and Refining Corporation amalgamated the assets of 11 small petroleum companies. Originally a New York corporation, Sinclair Oil reincorporated in Wyoming in 1976. The corporate logo featured the silhouette of a large green Apatosaurus dinosaur, based on the then-common idea that oil deposits beneath the earth came from the dead bodies of dinosaurs.

Harry Ford Sinclair was an American industrialist, and the founder of Sinclair Oil. He was implicated in the 1920s Teapot Dome scandal, and served six months in prison for contempt of Congress. Although this harmed his reputation, he returned to his former life and enjoyed its prosperity until his death.