Frontier Oil was an energy company, originally based in Canada, that moved to the United States.

Frontier's primary products were gasoline, diesel, and asphalt, and were marketed in the Rocky Mountain and Plains States.

Frontier Oil owned refineries in Cheyenne, Wyoming and El Dorado, Kansas.

The company was incorporated in Ontario in 1949 as Wainwright Refineries Limited, changing its names to Wainwright Producers & Refiners Limited in 1953, to Wainoco Oil and Chemicals Ltd. in 1966, and to Wainoco Oil Ltd. in 1971.

[4] In 1976 it became Wainoco Oil Corporation on its move to Wyoming in the United States.