Adam Opel AG (Opel) is a German automobile manufacturer headquartered in Rüsselsheim, Hesse, Germany and a subsidiary of the American General Motors Company. The company designs, engineers, manufactures and distributes Opel-branded passenger vehicles, light commercial vehicles and vehicle parts for distribution in Africa, Asia, Europe and South America.

Opel designed and manufactured vehicles are also sold under the Buick brand in the United States, Canada, Mexico and China, the Holden brand in Australia and New Zealand and the Vauxhall brand in the United Kingdom. Opel traces its roots to a sewing machine manufacturer founded by Adam Opel in 1862. The company began manufacturing bicycles in 1886 and produced its first automobile in 1899. Opel became a share-limited company (German: Aktiengesellschaft) in 1929; United States-based General Motors took a majority stake in Opel that same year. General Motors assumed full control in 1931 and today Adam Opel AG is a wholly owned subsidiary of General Motors Company. Although Adam Opel AG continues to be a share-limited company, shares of the company are not publicly listed. Adam Opel AG is the parent company of General Motors UK Limited, better known as Vauxhall, and various other General Motors subsidiaries. During the 1970s and 1980s, Opel and Vauxhall ranges were rationalised into one consistent range across Europe.