8mm is a motion picture film format wherein each frame of the film is eight millimeters wide. It exists in two versions: regular 8mm and Super 8, a slightly larger format that eventually became the prevalent version of the medium. Super 8 film magazines actually contain a 16mm-wide film with perforations along each edge, which is only exposed along half of its width. When the film reaches its end the magazine is turned over and the second half is exposed. During processing the film is split down the middle, resulting in two lengths of 8mm film, each with a single row of perforations along one edge.

Many independent filmmakers such as Derek Jarman have made extensive use of 8mm film with remarkable results.

8mm was originally a consumer format film, but has become more of a format for film students who wish to learn the basics of shooting film.

There is also an American film entitled 8mm about a private detective verifying the existence of a snuff movie.