Belle de Jour

Catherine Deneuve from Belle de Jour.

The 1967 French film was directed by Luis Buñuel and starred Catherine Deneuve, Jean Sorel, and Michel Piccoli.

It was 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. (Source)