The first Leica prototypes were built by Oskar Barnack at Ernst Leitz Optische Werke, Wetzlar, in 1913. Intended as a compact camera for landscape photography, particularly during mountain trips, the Leica was the first practical 35mm camera, using standard cinema 35 mm film. The Leica transports the film horizontally, extending the frame size to 24×36 mm, instead of the 18×24 mm used by cinema cameras which transported the film vertically, with a 2:3 aspect ratio.

The Leica went through several iterations, and in 1923 Barnack convinced his boss, Ernst Leitz II, to make a prototype series of 31. The camera was an immediate success when introduced at the 1925 Leipzig Spring Fair as the Leica I (for Leitz camera). The focal plane shutter had a range from 1/20 to 1/500 second, in addition to a Z for Zeit (time) position.

Early Leica cameras bear the initials D.R.P., which stands for Deutsches Reichspatent, the name for German patents before May 1945. This is probably a reference to German patent No. 384071 "Rollfilmkamera" granted to Ernst Leitz, Optische Werke in Wetzlar, on 3 November 1923.

Leica Camera AG is an international company in the optical industry, with its headquarters based in Solms, Germany, and a second location in Portugal. All products from the three divisions - Photography, Hunting Lenses and Nature Watching - have a shared mission: to deliver better images.