126 is the number given to a cartridge-based film format used in still photography. It was introduced by Kodak in 1963, and is associated mainly with low-end point-and-shoot cameras, particularly Kodak's own Instamatic series of cameras.

Although 126 was once very popular, as of 2008^[update] it is no longer manufactured, and few photofinishers will process it.

In 1963, Kodak introduced a new film, encased in a plastic cartridge, for which they re-introduced the "126" designation. (The number was originally used for the unrelated 126 roll film format from 1906 to 1949). The term "126" was intended to show that images were 26mm square, using Kodak's common 1xx film numbering system. However the image size is actually 28 × 28 mm, but usually reduced to approximately 26.5 × 26.5 mm by masking during printing or mounting.

The 126 film format was defined in ISO 3029, which has since been withdrawn.

Like the 120 format, there is a continuous backing paper, and the frame number is visible through a small window at the rear of the cartridge. Cameras for this type of film were equipped with a larger rectangular window in the back door, through which was visible not only the frame number, but also a portion of the label showing the film type and speed. The cartridge has a captive take-up spool, but no supply spool: the film and backing paper are simply coiled tightly and placed in the supply end of the cartridge. The positioning of the image is fixed by the cartridge. The film is 35mm wide, but unlike 135 film, it is unperforated, except for one registration hole per image, similar to the earlier 828 film. The camera is equipped with a sensing pin which falls into this hole when the film is fully advanced to the next frame, at which point the winding knob or lever is locked, so as to prevent winding past the pre-exposed frame lines.

A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects. The process of filmmaking has developed into an art form and industry.

Films are cultural artifacts created by specific cultures, which reflect those cultures, and, in turn, affect them. Film is considered to be an important art form, a source of popular entertainment and a powerful method for educating – or indoctrinating – citizens. The visual elements of cinema give motion pictures a universal power of communication. Some films have become popular worldwide attractions by using dubbing or subtitles that translate the dialogue into the language of the viewer.

Films are made up of a series of individual images called frames. When these images are shown rapidly in succession, a viewer has the illusion that motion is occurring. The viewer cannot see the flickering between frames due to an effect known as persistence of vision, whereby the eye retains a visual image for a fraction of a second after the source has been removed. Viewers perceive motion due to a psychological effect called beta movement.