Belle de Jour (pronounced [bɛl də ʒuʁ]) is a 1967 surrealist erotic psychological drama film directed by Luis Buñuel, and starring Catherine Deneuve, Jean Sorel, and Michel Piccoli. Based on the 1928 novel Belle de Jour by Joseph Kessel, the film is about a young woman who spends her midweek afternoons as a high-class prostitute, while her husband is at work.

The title of the film is a play on words on the French term belle de nuit ("beauty of the night", i.e., a prostitute), as Séverine works during the day under the pseudonym "Belle de Jour". Her nickname can also be interpreted as a reference to the French name of the morning glory (Convolvulaceae), meaning "beauty of [the] day", a flower that blooms only during the day.

Belle de Jour is one of Buñuel's most successful and famous films. It was Deneuve's second acclaimed success after The Umbrellas of Cherbourg. It won the Golden Lion and the Pasinetti Award for Best Film at the Venice Film Festival in 1967.