Rusalka is an opera by Antonín Dvor(ák. The Czech libretto was written by the poet Jaroslav Kvapil based on the fairy tales of Karel Jaromír Erben and Božena Ne(mcová; a Rusalka is a water sprite of Slavic mythology, usually inhabiting a lake or river). Rusalka is the one of the most successful Czech operas, and represents a foundation stone of the repertoire of Czech opera houses.