Gustave III, ou Le bal masqué is an opéra historique or grand opera in five acts by Daniel Auber, with a libretto by Eugène Scribe.

Grand opera is a genre of 19th-century opera generally in four or five acts, characterized by large-scale casts and orchestras. The original productions consisted of spectacular design and stage effects with plots normally based on or around dramatic historic events. The term is particularly applied to certain productions of the Paris Opéra from the late 1820s to around 1860; 'grand opéra' has sometimes been used to denote the Paris Opéra itself.