Duke of Valentinois (French: Duc de Valentinois; Italian: Duca Valentino) is a title of nobility, originally in the French peerage. It is currently one of the many hereditary titles claimed by the Prince of Monaco despite its extinction in French law in 1949. Though it originally indicated administrative control of the Duchy of Valentinois, based around the city of Valence, the duchy has since become part of France, making the title simply one of courtesy.
It has been created at least four times: on August 17, 1498, for Cesare Borgia, in 1548 for Diane of Poitiers, in 1642 for Prince Honoré II of Monaco, and most recently in 1715 for Prince Jacques I of Monaco.