motion picture made and distributed outside the commercial film industry, usually as an artistic expression of its maker, who often acts as its producer, director, writer, photographer, and editor. Underground films usually display greater freedom in form, technique, and content than films directed toward a mass audience and distributed through regular commercial outlets. The term underground film came into common use in the 1950s, when the greater availability of good-quality 16-millimetre film stock and equipment permitted an increasing number of nonprofessionals to engage in cinema art. The term was also applied to earlier films that were considered too experimental, too frank, or too esoteric for the general public, made both by professionals and by amateurs.

In the underground film the interplay of light and shadow basic to cinema art often takes precedence over narrative structure. The filmmaker ordinarily uses inexpensive production methods and a 16-millimetre or 8-millimetre camera. He may incorporate overexposures, underexposures, or triple exposures. Some underground films are purely abstract patterns of light and colour. Such films vary considerably in length. Robert Breer's A Miracle (1954) is 14 seconds long, while Andy Warhol, the most highly publicized of the underground filmmakers, did a study of the Empire State Building, Empire (1964), that lasts eight hours. During the 1920s filmmaking was stimulated by nonobjective art, represented by the Dadaist, Cubist, and Surrealist movements. Leading filmmakers such as Jean Renoir, René Clair, and Sergey Eisenstein made private experiments in addition to their publicly shown films. The classic Un Chien andalou (1928; “An Andalusian Dog”) by the director Luis Buñuel and the Surrealist artist Salvador Dalí, financed by Buñuel's mother, was a product of this period.

Little of comparable interest was produced until the late 1950s, when a host of new cinema artists arose in the United States. Unlike their predecessors, they were strongly influenced by the techniques and personal expression of commercial films by directors such as Jean-Luc Godard, Ingmar Bergman, and Federico Fellini. Jonas Mekas, Stan Brakhage, and Stan Vanderbeek were among the creative leaders of the movement, which grew rapidly. Students from newly established film departments in universities across the country released thousands of independently produced film experiments. Outstanding examples, such as Stan Vanderbeek's Breathdeath (1963–64) and Kenneth Anger's Scorpio Rising (1962–64), were seen over the years by a vast audience. In the 1970s underground filmmakers, many of whom had a background in painting or sculpture, continued to emphasize composition and form and an intensity of feeling rather than dramatic structure. Magic and the supernatural and political protest, traditionally popular topics in the underground, remained prominent among the great variety of subjects considered.