24 Hour Psycho is a 1993 art installation video by Scottish artist Douglas Gordon. It is an appropriation of Alfred Hitchcock's 1960 psychological thriller film Psycho, slowed down to approximately two frames per second from its original 24. As a result, the film lasts for precisely 24 hours, rather than the original running time of 109 minutes (1 hour, 49 minutes).

First shown in 1993 at Tramway Art Centre in Glasgow, Scotland, and at the Kunst-Werke Institute for Contemporary Art in Berlin, Germany, 24 Hour Psycho was Gordon's first work to showcase his theme of repetition. In 2008, Gordon created a second installation entitled 24 Hour Psycho Back and Forth and To and Fro, which consists of two simultaneous projections of 24 Hour Psycho placed side-by-side. One projection plays the film normally while the other plays it in reverse, briefly culminating in a convergence at the centre for an identical shot.