Donnie Darko is a 2001 American science fiction psychological thriller film written and directed by Richard Kelly in his directorial debut, and produced by Flower Films. It stars Jake Gyllenhaal, Jena Malone, Drew Barrymore, Mary McDonnell, Katharine Ross, Patrick Swayze, and Noah Wyle, with Seth Rogen in his film debut in a minor role. Set in October 1988, the film follows Donnie Darko (Gyllenhaal), a troubled teenager who inadvertently escapes a bizarre accident by sleepwalking. He has visions of Frank, a mysterious figure in a rabbit costume who informs him that the world will end in 28 days.

Development began in late 1997 when Kelly had graduated from film school and started writing scripts. He took an early idea of a jet engine falling onto a house with no one knowing its origin and built the story around it. Kelly insisted on directing the film himself and struggled to secure backing from producers until 2000, when Pandora Cinema and Barrymore's Flower Films agreed to produce it on a $4.5 million budget. Filming took 28 days in the summer of 2000, mostly in California. The soundtrack features a cover of "Mad World" by Tears for Fears by American musicians Gary Jules and Michael Andrews, which went to No. 1 on the UK Singles Chart for three weeks and was the Christmas number 1 in 2003.

Donnie Darko premiered at the Sundance Film Festival on January 19, 2001, followed by a limited theatrical release on October 26. Because the film's advertising featured a crashing plane and the September 11 attacks had occurred a month and a half before, it was scarcely advertised. This affected its box office performance and it grossed just $517,375 in its initial run. However, the film gained a cult following, and after reissues, it went on to gross $7.5 million worldwide, and earned more than $10 million in US home video sales. It was listed No. 2 in Empire's "50 Greatest Independent Films of All Time," and No. 53 in Empire's "500 Greatest Movies of All Time." Kelly released Donnie Darko: The Director's Cut in 2004. The film was adapted into a stage production in 2007 and a sequel, S. Darko, followed in 2009 without Kelly's involvement. In 2021, he announced that work on a new sequel is in progress.