Haydée, ou Le secret is an opéra comique by the French composer Daniel Auber, first performed by the Théâtre Royal de l'Opéra-Comique at the Salle Favart in Paris on 28 December 1847.

The libretto (in three acts) is by Auber's regular collaborator, Eugène Scribe and is based on a short story by Prosper Mérimée, La Partie de trictrac (1830).

The title character is a Cypriot slave girl; her name is taken from Haidée, the pirate king's daughter, in Byron's poem Don Juan.

Malipieri overhears Lorédan talking in his sleep about a great crime in his past: in his youth, he cheated at dice in order to win the fortune of the Venetian senator Donato, who then killed himself.

Malipieri darkly threatens to expose Lorédan's crime, demanding Haydée's hand in marriage in order to keep silent, and reveals she is really a princess.