The Act of Killing is a documentary film on the Indonesian genocide that took place between October 1965 and March 1966, during which time an estimated 500,000 to 2.5 million accused communists, including landless farmers, unionized workers, labour organizers, intellectuals and ethnic Chinese Indonesians, were killed. However, much of the film is dedicated to fictional re-enactments of the 1965–66 killings.

Oppenheimer's approach is to bring into relief the contours of the extermination of communists in Indonesia by inviting former death-squad leaders and paramilitary gangsters to re-enact the killings in whatever ways they choose. They opt at times for a realist aesthetic and at other times for genres as diverse as Hollywood westerns, film noir gangster movies, and glitzy musicals.

The text explores the aesthetic and political consequences springing from this modality of representation while comparing the film to other representative testimonial documentaries of genocides and extermination.