The Act of Killing is a 2012 experimental documentary film directed by Joshua Oppenheimer, with Christine Cynn and an anonymous Indonesian co-directing. The film follows individuals who participated in the Indonesian mass killings of 1965–66, wherein alleged communists and people against the New Order regime were tortured and killed, with the killers, many becoming gangsters, still in power throughout the country. The film was mostly filmed in Medan, North Sumatra, following the executioner Anwar Congo and his acquaintances as they, upon Oppenheimer's request, re-enact their killings and talk about their actions openly, also following Congo's psychological journey facing the topic.

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".