Robert Joseph Flaherty, was an American filmmaker who directed and produced the first commercially successful feature-length documentary film, Nanook of the North (1922). The film made his reputation and nothing in his later life fully equaled its success, although he continued the development of this new genre of narrative documentary with Moana (1926), set in the South Seas, and Man of Aran (1934), filmed in Ireland's Aran Islands. Flaherty is considered the father of both the documentary and the ethnographic film.

A documentary film or documentary is a non-fictional motion picture intended to "document reality, primarily for instruction, education or maintaining a historical record". Bill Nichols has characterized the documentary in terms of "a filmmaking practice, a cinematic tradition, and mode of audience reception [that remains] a practice without clear boundaries".