The French Opera House, or Théâtre de l'Opéra, was an opera house in New Orleans. It was one of the city's landmarks from its opening in 1859 until it was destroyed by fire in 1919. It stood in the French Quarter at the uptown lake corner of Bourbon and Toulouse Streets, with the main entrance on Bourbon. The site is currently occupied by the Four Points by Sheraton French Quarter.

Le roi d'Ys is an opera in three acts and five tableaux by the French composer Édouard Lalo, to a libretto by Édouard Blau, based on the old Breton legend of the drowned city of Ys. That city was, according to the legend, the capital of the kingdom of Cornouaille.