Les Diaboliques (French: [le djabɔlik], released as Diabolique in the United States and variously translated as The Devils or The Fiends) is a 1955 French psychological horror thriller film co-written and directed by Henri-Georges Clouzot, starring Simone Signoret, Véra Clouzot, Paul Meurisse and Charles Vanel. It is based on the 1952 novel She Who Was No More (Celle qui n'était plus) by Pierre Boileau and Thomas Narcejac.

The story blends elements of thriller and horror, with the plot focusing on a woman and her husband's mistress who conspire to murder the man. It was the 10th highest-grossing film of the year in , with a total of 3,674,380 issions. The film also received the 1954 Louis Delluc Prize.

Clouzot, after finishing The Wages of Fear (1953), optioned the screenplay rights, preventing Alfred Hitchcock from making the film. The film helped inspire Hitchcock's Psycho (1960). Robert Bloch, the author of the novel Psycho, stated in an interview that his all-time favorite horror film was Les Diaboliques.