Exxon Mobil Corporation (NYSE: XOM) was America's biggest publicly traded oil and gas company in 2019, and one of the largest companies in any industry. It reported consolidated revenue of more than $290 billion in 2018 across its worldwide upstream and downstream oil and gas operations. As of November 2019, it had a market capitalization of about $293 billion.

Exxon Mobil's core businesses include oil and gas exploration and production, petroleum refining, chemical manufacturing, and the marketing of petroleum and chemical products. Petroleum products are primarily marketed under the Exxon brand in the United States, while the company's Esso brand is used in most international markets. The Mobil and Mobil 1 brands are used in the U.S. and internationally.

Many of Exxon Mobil's core operations are organized under international subsidiaries. They include ExxonMobil France Holding SAS, ExxonMobil Australia, and Esso Petroleum Company Limited in the United Kingdom. In addition to its core subsidiaries, Exxon Mobil owns numerous other companies, including wholly-owned subsidiaries, joint ventures, and affiliates.

1. Imperial Oil Ltd.

Imperial Oil Limited is a publicly listed oil and gas company in Canada. As of 2019, Exxon Mobil owned about 70% of the company's outstanding shares. Imperial Oil operates along the full length of the oil and gas supply chain. The company has oil and gas exploration and production operations across Canada. Imperial Oil ranks as the biggest oil refiner in the country. It is also one of the largest chemical producers in Canada. Additionally, Imperial Oil markets petroleum products through its network of more than 1,700 gasoline service stations operating under Exxon Mobil's Esso brand.

2. XTO Energy, Inc.

XTO Energy, Inc. is an oil and gas drilling company in the United States. It specializes in extracting natural gas from shale formations, often using a process known as hydraulic fracturing. The company has operated as a wholly-owned subsidiary of Exxon Mobil since it was acquired for $31 billion in 2010. The merging of the two companies lifted Exxon Mobil into the position as the top natural gas producer in the United States. However, then Exxon CEO Rex Tillerson later conceded, "We probably paid too much."

3. Mobil Producing Nigeria Unlimited

Mobil Producing Nigeria Unlimited (MPN) is one of the largest oil exploration and production companies in Nigeria, which itself is the biggest oil-producing country in Africa. MPN operates as a joint venture with the state-owned Nigerian National Petroleum Corporation. MPN holds a 40% stake in the joint venture, while the Nigerian federal government owns the remaining 60%. In 2018, the joint venture produced more than 550,000 barrels of oil per day. Plans are in place to raise production to more than 1 million barrels per day.

4. Aera Energy LLC

Aera Energy LLC is an oil and gas producer based in California. The company was established in 1997 and is co-owned by Exxon Mobil and Royal Dutch Shell PLC. Aera Energy operates as an independent entity under the direction of its own board of managers. The company produces approximately 32 million cubic feet of natural gas and 125,000 barrels of oil per day in several California counties. In total, Aera produces around 25% of the oil and gas extracted in California.

5. Exxon Neftegas Ltd.

Exxon Neftegas Limited is a subsidiary of Exxon mobile operating in Russia and incorporated in the Bahamas. Exxon Neftegas focuses on developing the oil and natural gas resources of Sakhalin Island, which is off the east coast of Russia and north of Japan. Exxon Neftegas owns a 30% stake in the Sakhalin-1 project. The Sakhalin-1 area has estimated reserves of 17.1 trillion cubic feet of natural gas and 2.3 billion barrels of oil that can be extracted.