Que la fête commence... (English title Let Joy Reign Supreme) is a 1975 French film directed by Bertrand Tavernier and starring Philippe Noiret.

It is a historical drama set during the 18th century French Régence centring on the Breton Pontcallec Conspiracy.

To assist him, Philippe enlists the aid of an atheistic and venal priest named Guillaume Dubois, another libertine who does not care for anyone except himself.

The film begins with the gruesome autopsy of Marie Louise Élisabeth d'Orléans, Duchess of Berry, elder daughter of the Regent who died on 21 July 1719, her health fatally ruined by her debauched life and a series of clandestine pregnancies.

Notoriously promiscuous, Joufflotte ("chubby")—as she was nicknamed because of her generous proportions—was rumoured to have committed incest with her father.