Julietta is an opera by Bohuslav Martinů, who also wrote the libretto, in French, based on the play Juliette ou la Clé des songes (Juliette, or The Key of Dreams) by the French author Georges Neveux. A libretto in Czech was later prepared for its premiere which took place at the Prague National Theatre on 16 March 1938. Julietta has become widely considered as Martinů's masterpiece.[1]