Ultramar is an Eastern Canadian gas and home fuel retailer, with its head office located in Montreal, Quebec. Ultramar operates gas stations and home fuel delivery in Ontario, Quebec, and Atlantic Canada.

British oil company Ultramar plc established operations in Canada in 1961. Retail stations were originally branded "Golden Eagle". Its refinery in Lévis, Quebec was built ten years later.

From 1979 to 1996, Ultramar grew by acquiring stations from several other companies, including Canadian fuel marketers Texaco Canada, Gulf Canada, Sergaz, Sunoco and Spur.

In 1981, Ultramar acquired Hanford, California-based Beacon Oil Company. It retained the name.

In 1990, it acquired the Dartmouth, Nova Scotia refinery with the purchase of other assets of Texaco Canada.

In 1991, Lasmo, a British oil company, bought Ultramar plc and in 1992 Lasmo spun off the North American refining and marketing operations which became known as Ultramar Corporation.

In 1994, Ultramar acquired Sergaz (founded in 1971 by André Ducharme) and Sunoco's Quebec gas stations. Some gas stations still operate under Sergaz but most were closed.

In 1996, Ultramar Corporation merged with Diamond Shamrock to form Ultramar Diamond Shamrock.