This subseries documents Opel, which was built by Adam Opel of Rüsselheim, Germany (1898-1928) and Adam Opel AG of Rüsselheim, Germany (1928-Present). Opel was founded by Adam Opel in 1862. Originally a manufacturer of sewing machines and bicycles, the company built its first car in 1899. Opel quickly grew and became Germany's largest automaker by 1914.

During the 1920s, the firm became the first German automaker to mass produce vehicles on an assembly line. General Motors Corporation bought a controlling interest in Opel in 1929 and acquired full ownership of the firm 1931. Opel was seized Germany's Nazi government in 1940, but General Motors formally regained control of it in 1948. General Motors consolidated Opel's operations with those of Vauxhall during the 1970s and 1980s.

Opel is Germany's second oldest and fourth largest automaker. It is currently a subsidiary of General Motors Corporation and produces a wide of vehicles. See also General Motors, General Motors (Europe), and Vauxhall (United Kingdom).