'Le Roi d'Ys' (The King of Ys) is an opera in three acts by the French composer Édouard Lalo, to a libretto by Édouard Blau, based on the old Breton legend of the drowned city of Ys, which was, according to the legend, the capital of the kingdom of Cornouaille. Apart from the overture, the most famous piece in the opera is the tenor's aubade in act 3, 'Vainement, ma bien aimée' which crops up from time to time in recitals and competitions.
