Belle de Jour

It is possibly the best-known erotic film of modern times, perhaps the best. That's because it understands eroticism from the inside-out—understands how it exists not in sweat and skin, but in the imagination.

—Roger Ebert

Belle de Jour is one of the most famous films directed by Luis Buñuel. Released in 1967, it starred then-débutante Catherine Deneuve.

Séverine (Deneuve) looks outwardly like the perfect Housewife. Beautiful, demure, well-mannered and impeccably groomed, she is the very image of bourgeois propriety. In fact she is a masochist who likes to fantasize about being humiliated and treated like a sex object. On the recommendation of a friend, she acts out on these fantasies by becoming a part-time prostitute in an upscale brothel. Since she only turns tricks during her husband's business hours, she is given the moniker Belle de Jour, "daytime beauty".

Tropes used in Belle de Jour include:

All Girls Want Bad Boys
All Just a Dream: It's unclear what really happens and what just takes place in Séverine's overactive fantasy life.
All Women Are Prudes: Subverted hard.
Band of Brothels: Séverine's "colleagues".
Bastard Boyfriend: Marcel.
Blonde, Brunette, Redhead: Séverine and her fellow prostitutes.
Covert Pervert: Séverine.
Defrosting Ice Queen: Bunuel deliberately used Deneuve's appearance as a blond ice queen to emphasize the contrast between her straight-laced persona and her real inner self.
Fetish: Séverine's is to be tied up and sexually abused by strangers.
Foreshadowing: Pierre reflecting upon a wheelchair. At the end of the movie, he's paraplegic.
Gainax Ending: Not even Luis Bunuel himself was entirely sure what it meant.
"It's Not Rape If You Enjoyed It": Séverine's first job.
Les Yay: The madam is obviously attracted to Séverine, though the latter feels ambivalent about it.
The Mafia: Marcel and another client are part of it.
Murder the Hypotenuse: Marcel attempts this on Séverine's husband. Doesn't work, and he gets killed in the process.
Riddle for the Ages: One customer shows up with a small lacquered box, the contents of which cause a prostitute to recoil in shock. We'll never know what's in it.
Sexless Marriage
Yandere: Marcel.