Illusions perdues — in English, Lost Illusions — is a serial novel written by the French writer Honoré de Balzac between 1837 and 1843. It consists of three parts, starting in provincial France, thereafter moving to Paris, and finally returning to the provinces. The book resembles another of Balzac's greatest novels, La Rabouilleuse, that is set in Paris and in the provinces. It forms part of the Scènes de la vie de province in La Comédie humaine.

Honoré de Balzac was a French novelist and playwright. The novel sequence La Comédie humaine, which presents a panorama of post-Napoleonic French life, is generally viewed as his magnum opus.