Rusalka, Op. 114, is an opera by Antonín Dvořák. His ninth opera (1900–1901), it became his most successful, frequenting the standard repertoire worldwide. Jaroslav Kvapil wrote the libretto on Karel Jaromír Erben's and Božena Němcová's fairy tales. The rusalka is a water sprite from Slavic mythology; it usually inhabits a lake or river.