Psycho III is a 1986 American slasher film, and the third film in the Psycho franchise. It stars Anthony Perkins, who also directs the film, reprising the role of Norman Bates. It co-stars Diana Scarwid, Jeff Fahey, and Roberta Maxwell. The screenplay is written by Charles Edward Pogue. The original electronic music score is composed and performed by Carter Burwell in one of his earliest projects. Psycho III is unrelated to Robert Bloch's third Psycho novel, Psycho House, which was not published until 1990.

The film takes place one month after the events of Psycho II where Norman Bates is still running the Bates Motel with the corpse of Emma Spool still sitting up in the house. A suicidal nun, with whom Norman falls in love, comes to the motel along with a drifter named Duane Duke. A reporter also tries to solve the mysterious disappearance of Mrs. Spool as someone begins another murder spree.

Released on July 2, 1986, Psycho III grossed $14.4 million at the U.S. box office on a budget of $8.4 million, becoming the lowest-grossing film in the series. It received mixed reviews from critics and was followed by a television prequel, Psycho IV: The Beginning, which was released on Showtime in November 1990. Later in 1987, Perkins' performance in this third installment of the Psycho screen anthology would garner him a Saturn Award nomination for Best Actor, and the film itself would also be nominated for a Saturn Award for Best Horror Film.