Le roi d'Ys is an opera in three acts by the French composer Édouard Lalo, to a libretto by Édouard Blau. It is 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. The opera includes a noteworthy aubade for tenor in act 3, titled "Vainement, ma bien-aimée" (In vain, my beloved). Le roi d'Ys premiered on 7 May 1888 at the Théâtre Lyrique in Paris, in a production by the Opéra-Comique. Within France, the opera was regarded as Lalo's most recognized work. This poster was produced by Auguste François-Marie Gorguet for the 1888 premiere of Le roi d'Ys, and depicts the final scene of the opera.Poster credit: Auguste François-Marie Gorguet; restored by Adam Cuerden