Exxon acquired Mobil in 1999, creating ExxonMobil in a deal valued at about $81 billion.
The companies announced their merger in December 1998, and shareholders approved it in 1999. The transaction combined two descendants of John D. Rockefeller's Standard Oil empire. Exxon had previously been known as Standard Oil of New Jersey, while Mobil descended from Standard Oil of New York.
The merger created ExxonMobil, one of the world's largest publicly traded oil and gas companies. It combined exploration and production operations with refining, fuels, lubricants and chemical businesses. Because the companies were major competitors, regulators required asset sales, including the divestiture of some stations and refinery interests.
The transaction is often confused with the later Chevron-Texaco merger, which was announced in 2000. ExxonMobil's name preserves both corporate identities, but Exxon was the acquiring company in the 1999 combination.