Belle de Jour (pronounced [bɛl də ʒuʁ]) is a 1967 surrealist erotic psychological drama film directed by Luis Buñuel, from a screenplay he co-wrote with Jean-Claude Carrière. Based on the 1928 novel of the same name by Joseph Kessel, the film stars Catherine Deneuve in the leading role, a young housewife who spends her midweek afternoons as a high-class prostitute, while her husband is at work. It co-stars Jean Sorel, and Michel Piccoli, and features Geneviève Page, Francisco Rabal, Pierre Clémenti, Francis Blanche and Georges Marchal in supporting roles.

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. Deneuve was nominated for BAFTA Award for Best Actress in a Leading Role.