Rusalka is an opera by Antonín Dvořák. The Czech libretto was written by the poet Jaroslav Kvapil based on the fairy tales of Karel Jaromír Erben and Božena Němcová. Rusalka is one of the most successful Czech operas, and represents a cornerstone of the repertoire of Czech opera houses. A Rusalka is a water sprite from Slavic mythology, usually inhabiting a lake or river.

This popular excerpt from Rusalka is the "Song to the Moon" ("Měsíčku na nebi hlubokém") from Act 1 which is often performed in concert and recorded separately. It has also been arranged for violin and used on film sound tracks.