American Psycho is a 2000 satirical horror film directed by Mary Harron, who co-wrote the screenplay with Guinevere Turner. Based on the 1991 novel by Bret Easton Ellis, it stars Christian Bale as Patrick Bateman, a New York City investment banker who leads a double life as a serial killer alongside an ensemble cast of Willem Dafoe, Jared Leto, Josh Lucas, Chloë Sevigny, Samantha Mathis, Cara Seymour, Justin Theroux, and Reese Witherspoon. The film blends horror and black comedy to satirize 1980s yuppie culture and consumerism, exemplified by Bateman.

Easton considered his controversial novel unfilmable but producer Edward R. Pressman was determined to adapt it and bought the film rights in 1992. Stuart Gordon, David Cronenberg and Rob Weiss considered directing the film before Harron and Turner began writing the screenplay in 1996. They sought to make a 1980s period film that emphasized the novel's satire. The pre-production period was tumultuous as Harron chose Bale to play Bateman but because distributor Lions Gate Films sought Leonardo DiCaprio in the role, Harron was fired and replaced with Oliver Stone. After DiCaprio and Stone left due to creative differences, Harron was rehired and allowed to cast Bale. Principal photography began in February 1999 in Toronto and New York City.

American Psycho premiered at the Sundance Film Festival on January 21, 2000 and was theatrically released in the United States on April 14. The film received mostly positive reviews with praise for Bale's performance and the screenplay, grossing $34 million on a $7 million budget. It has since developed a cult following and a strong presence in meme culture since the 2010s. A direct-to-video sequel, American Psycho 2, was released in 2002, although it has little relation to the original. A new adaptation of the novel, directed by Luca Guadagnino, is currently in the works.