Opel Automobile GmbH (German pronunciation: [ˈoːpl̩]), usually shortened to Opel, is a German automobile manufacturer which has been a subsidiary of Stellantis since 16 January 2021. It was owned by the American automaker General Motors from 1929 until 2017 and the PSA Group prior to its merger with Fiat Chrysler Automobiles to form Stellantis in 2021. Most of the Opel lineup is marketed under the Vauxhall brand in the United Kingdom since the 1980s. Some Opel vehicles were badge-engineered in Australia under the Holden brand until 2020, in North America and China under the Buick, Saturn (until 2010), and Cadillac brands, and in South America under the Chevrolet brand.

Opel traces its roots to a sewing machine manufacturer founded by Adam Opel in 1862 in Rüsselsheim am Main. The company began manufacturing bicycles in 1886 and produced its first automobile in 1899. With the Opel RAK program, the world's first rocket program, under the leadership of Fritz von Opel, the company played an important role in the history of aviation and spaceflight: Various land speed records were achieved, and the world's first rocket-powered flights were performed in 1928 and 1929. After listing on the stock market in 1929, General Motors took a majority stake in Opel and then full control in 1931, making the automaker a wholly owned subsidiary, establishing an American ownership of the German automaker for nearly 90 years. Together with British manufacturer Vauxhall Motors, which GM had acquired in 1925, the two companies formed the backbone of GM's European operations – later merged formally in the 1980s as General Motors Europe.

In March 2017, PSA Peugeot Citroën agreed to acquire Opel, the British twin sister brand Vauxhall and the European auto lending business from General Motors for €2 billion ($2.3 billion), making the French automaker the second biggest in Europe, after Volkswagen.

Opel is still headquartered in Rüsselsheim am Main. The company designs, engineers, manufactures, and distributes Opel-branded passenger vehicles, light commercial vehicles, and vehicle parts; together with its British sister marque Vauxhall, they are present in over 60 countries around the world.