Psycho is a 1960 American horror film produced and directed by Alfred Hitchcock. The screenplay, written by Joseph Stefano, was based on the 1959 novel of the same name by Robert Bloch. The film stars Anthony Perkins, Janet Leigh, Vera Miles, John Gavin and Martin Balsam. The plot centers on an encounter between on-the-run embezzler Marion Crane (Leigh) and shy motel proprietor Norman Bates (Perkins) and its aftermath, in which a private investigator (Balsam), Marion's lover Sam Loomis (Gavin) and her sister Lila (Miles) investigate her disappearance.

Psycho was seen as a departure from Hitchcock's previous film, North by Northwest (1959), as it was filmed on a small budget in black-and-white by the crew of his television series Alfred Hitchcock Presents. Initially, the film divided critics due to its controversial subject matter, but audience interest and outstanding box-office returns prompted a major critical re-evaluation. Psycho was nominated for four Academy Awards, including Best Director for Hitchcock and Best Supporting Actress for Leigh.

Psycho is now considered one of Hitchcock's best films, and is arguably his most famous and influential work. It has been hailed as a major work of cinematic art by international film critics and scholars who praise its slick direction, tense atmosphere, impressive camerawork, memorable score and iconic performances. It is regarded as "the most heavily analyzed film in the long career of the most investigated director in the history of American film" and often ranked among the greatest films of all time, it set a new level of acceptability for violence, deviant behavior and sexuality in American films, and has been considered to be one of the earliest examples of the slasher film genre. After Hitchcock's death in 1980, Universal Pictures produced follow-ups: three sequels, a remake, a made-for-television spin-off and a television series. In 1992, the Library of Congress deemed the film "culturally, historically, or aesthetically significant" and selected it for preservation in the United States National Film Registry.