Suncor Energy

In 1979, Sun formed Suncor by merging its Canadian refining and retailing interests; Great Canadian Oil Sands (a majority-owned subsidiary, which constructed and operated the first commercial plant to develop Canada's Athabasca oil sands and went on production in 1967); and its conventional oil and gas interests. In 1981, the Government of Ontario purchased a 25% stake in the company; it divested in 1993. In 1995 Sun Oil also divested its interest in the company, although Suncor maintained the Sunoco retail brand in Canada. With these two divestitures, Suncor become an independent, widely held public company.

In 2003, Suncor acquired a refinery and associated Phillips 66 gas stations in Commerce City, Colorado from ConocoPhillips. In 2005, Suncor acquired a second Commerce City refinery from Valero Energy. Suncor moved its retail brand from Phillips 66 to Shell from 2009 to 2013. Suncor added the Exxon and Mobil brands in Colorado and Wyoming in 2015.

On March 23, 2009, Suncor announced its intent to acquire Petro-Canada. This merger created a company with a combined market capitalization of C$43.3 billion. On June 4, 2009, a 98% approval rate was reached by Suncor's shareholders for the acquisition of Petro-Canada and the Competition Bureau approved the merger on June 21, 2009. The merger with Canada's 11th largest company was completed on August 1, 2009 in a $21 billion deal to form the second-largest company in Canada (after Royal Bank of Canada) in terms of market capitalization. In December 2009, as a condition of the merger, Suncor sold 98 gas stations in Ontario to Husky Energy, consisting of 68 Sunoco-branded locations and 30 Petro-Canada-branded locations.

In 2015, Suncor courted Canadian Oil Sands, the largest owner of the Syncrude project with 37% ownership (compared with Suncor's 12%), with proposals for acquisition and hostile takeover. In January 2016 they reached an agreement with Suncor acquiring COS for C$6.6 billion, raising its Syncrude ownership to 49%.

On April 27, 2016, Suncor announced that it had reached a $937-million deal to acquire Murphy Oil's 5% stake in the Syncrude project, growing its interest in Syncrude to nearly 54%, making it the majority shareholder of the project. In fall 2021, Suncor assumed operatorship of the Syncrude Joint Venture oil sands project in a bid to improve its performance. Suncor holds a majority stake in Syncrude with 58.74 per cent.

In July 2022, president and CEO Mark Little resigned amid investor pressure and after a series of workplace deaths and safety incidents. Executive vice-president for downstream Kris Smith was named as interim CEO. On February 21, 2023, Suncor announced that former Imperial Oil Ltd. president and CEO Rich Kruger had been named its new chief executive officer after a months-long search. Kruger replaced interim Suncor CEO Kris Smith on April 3, 2023. Smith assumed the role of chief financial officer and executive vice-president of corporate development after Suncor's annual general meeting on May 9, 2023.

June 2023 transactions with customers and suppliers were impaired due to a cyber attack. The company stated no customer information was stolen but some of the company's services, such as digital payment, crashed.

In October 2023, Suncor Energy acquired TotalEnergies' Canadian operations for C$1.47 billion($1.07 billion).

In North America, Suncor develops and produces oil and natural gas in Western Canada, Colorado, and offshore drilling in eastern Canada. Its international efforts include offshore developments in the North Sea, and conventional, land-based efforts in Libya, Syria, and Trinidad and Tobago.

Suncor operates refineries in Edmonton, Alberta; Sarnia, Ontario; Montreal, Quebec and Commerce City, Colorado. These refineries supply industrial, retail and commercial consumers. The company is also one of the largest Canadian retailers of petroleum products.

Upstream

Suncor is the world's largest producer of bitumen, and owns and operates an oil sands upgrading plant near Fort McMurray, Alberta, Canada. Originally developed by Great Canadian Oil Sands, a majority-owned subsidiary of Sun Oil, it is now wholly owned by the independent Suncor. It was the first commercial development on the Athabasca oil sands, although small, earlier projects like that at Bitumount also played a role in development. The company held a 36.75% interest in the Joslyn north oil sands project which was shelved pending an economic review by operator Total S.A. in May 2014. The Joslyn project was sold to CNRL in September 2018. The company also produces conventional oil, heavy crude oil, and natural gas.

Refining

In Canada, Suncor operates refineries in Alberta, Ontario and Quebec. The company's 135,000-barrel-per-day Strathcona, refinery runs entirely on oil sands-based feedstocks and produces a high-yield of light oils. A 137,000-barrel-per-day Montreal Refinery produces gasoline, distillates, asphalts, heavy fuel oil, petrochemicals, solvents and feedstock for lubricants. An 85,000-barrel-per-day refinery in Sarnia, Ontario produces gasoline, kerosene, jet and diesel fuels. A 98,000-barrel-per-day refinery in Commerce City, Colorado produces gasoline, diesel fuel and paving-grade asphalt.