Trianon (trēänôNˈ) [key], two small châteaux in the park of Versailles, Seine-et-Oise dept., N France. The Grand Trianon was built by J. H. Mansart in 1687 for Louis XIV; Napoleon I sometimes used it as a retreat. The Petit Trianon was built in 1762 by J. A. Gabriel for Louis XV. It was a favorite residence of Marie Antoinette and of the Empress Eugénie.