ExxonMobil Corporation (commonly shortened to Exxon) is an American multinational oil and gas corporation headquartered in Irving, Texas. It is the largest direct descendant of John D. Rockefeller's Standard Oil, and was formed on November 30, 1999, by the merger of Exxon and Mobil. Both of its predecessors are used as brands for fueling stations and downstream products today, alongside Esso. The vertically-integrated company also has a chemical division, ExxonMobil Chemical, which produces plastic, synthetic rubber, and other chemical products. ExxonMobil is incorporated in New Jersey.ExxonMobil's earliest corporate ancestor was Vacuum Oil Company, though Standard Oil is its largest ancestor prior to its breakup. The entity today known as ExxonMobil grew out of the Standard Oil Company of New Jersey (or Jersey Standard for short), the corporate entity which effectively controlled all of Standard Oil prior to its breakup. Jersey Standard grew alongside and with extensive partnership another Standard Oil descendant and its future merger partner, the Standard Oil Company of New York (Socony), both of which grew bigger by merging with various third companies like Humble Oil (which merged with Jersey Standard) and Vacuum Oil (merged with Socony). Both companies underwent rebranding in the 1960s and early 1970s, and by the time of the 1999 merger, Jersey Standard had been known as Exxon, and Socony known as Mobil. The merger agreement between Exxon and Mobil stipulated that Exxon would buy Mobil and rebrand as ExxonMobil, with Mobil's CEO becoming the vice-chairman of the company.One of the world's largest companies by revenue, ExxonMobil since its merger varied from the first to tenth largest publicly traded company by revenue, and has one of the largest market capitalizations out of any company. As of 2022, in the most recent rankings released in the Fortune 500, ExxonMobil was ranked sixth, and twelfth on the Fortune Global 500. ExxonMobil is the largest investor-owned oil company in the world, the largest oil company headquartered in the Western world, and the largest of the Big Oil companies in both production and market value. ExxonMobil's reserves were 20 billion BOE at the end of 2016 and the 2007 rates of production were expected to last more than 14 years. With 21 oil refineries constituting a combined daily refining capacity of 4.9 million barrels (780,000 m3), ExxonMobil is the second largest oil refiner in the world, trailing only Sinopec. Approximately 55.56% of the company's shares are held by institutions, the largest of which as of 2019 were The Vanguard Group (8.15%), BlackRock (6.61%), and State Street Corporation (4.83%).

ExxonMobil had been criticized for its slow response to cleanup efforts after the 1989 Exxon Valdez oil spill in Alaska, considered to be one of the world's worst oil spills in terms of damage to the environment. ExxonMobil has a history of lobbying for climate change denial and against the scientific consensus that global warming is caused by the burning of fossil fuels. The company has also been the target of accusations of improperly dealing with human rights issues, influence on American foreign policy, and its impact on various societies across the world.

Exxon Corporation, formerly known as the Standard Oil Company of New Jersey until 1973, was an American oil company and descendant of Standard Oil which merged with Mobil to form ExxonMobil in 1999. Once one of the Seven Sisters that dominated the global petroleum industry, Exxon was one of the largest companies in the world, being one of the top five companies on Fortune 500 between the first edition of the list and the year of its merger with Mobil and reaching the #1 spot on the list a few years between 1970 and 1995.Today, Exxon is used as a brand name for some gas stations operated by the now-merged company, as well as for downstream operations selling motor fuel and related products (the highest concentration of which are located in New Jersey, Pennsylvania, Texas and in the Mid-Atlantic and Southeastern states).