8 mm film is a motion picture film format where the filmstrip is eight millimeters wide. It exists in three versions: regular or standard 8 mm (the subject of this article); Super 8, a slightly larger format that eventually became the prevalent version of the medium; and Single8.

The standard 8 mm film format was developed by the Eastman Kodak company during the Great Depression and released on the market in 1932 to create a home movie format less expensive than 16 mm. The film spools actually contain a 16 mm film with twice as many perforations along each edge than normal 16 mm film, which is only exposed along half of its width. When the film reaches its end in the takeup spool, the camera is opened and the spools in the camera are flipped and swapped (the design of the spool hole ensures that this happens properly) and the same film is exposed along the side of the film left unexposed on the first loading. During processing, the film is split down the middle, resulting in two lengths of 8 mm film, each with a single row of perforations along one edge, so fitting four times as many frames in the same amount of 16 mm film. Because the spool was reversed after filming on one side to allow filming on the other side the format was sometime called Double 8. The framesize of 8 mm is 4,8 x 3,5 mm and 1 m film contains 264 pictures. Normally Double8 is filmed at 16 frame/s.

Common length film spools allowed to film about 3 to 4 min at 12, 15, 16 and 18 frames per second.

In 1965 Super 8 mm film, was introduced, with a smaller sprocket hole. This created a slightly larger picture area and an easy cartridge-loading system obviating the need to swap film spools. Kodak ceased producing standard 8 mm film in the early 1990s. Black and white 8 mm film is still manufactured in the Czech Republic, and several companies buy bulk quantities of 16 mm film to make regular 8 mm by re-perforating the stock, cutting it into 25 foot (7.6 m) lengths, and collecting it into special standard 8 mm spools which they then sell. Re-perforation requires special equipment. Some specialists also produce super 8 mm film from exisiting 16 mm, or even 35 mm film stock.

While Kodak super 8 mm cartridges cannot be reloaded, a reloadable cartridge was manufactured in the former USSR, probably in Ukraine where many Russian cameras were manufactured.

Super8 mm film is still produced by Kodak, and Pro8 mm. Fuji still produces Single8 film, which uses a different, proprietary cartridge format, but can be projected on all Super8 mm projectors. Double super8 mm film is also manufactured. This is 16 mm wide film but with super 8 mm size sprockets. It is used in the same way a standard 8 mm film in that the film is run through the camera twice and split down the middle to produce 8 mm film for projection. It is preferred by serious film makers because the registration in the camera is controlled by the precision camera equipment rather than the mass produced cartridge in which super8mm film is provided. Single 8 mm film from Fuji, which is dimensionally exactly the same as super 8 mm, has a cartridge system that used the precision gate of the camera rather than a built in version on the cartridge.