Sadko (Садко in Russian) is an opera by Nikolai Rimsky-Korsakov. The libretto is by both the composer and Vladimir Byelsky . Sadko was premiered on 7 January 1898 in Moscow.

The opera tells the story of Sadko, a troubador, who leaves his wife, Lubava, and home in Novgorod and eventually returns a wealthy man. During his years of travel he amasses a fortune, weds the daughter of the King and Queen of the Ocean and has other adventures. Upon his return, the city and Lubava rejoice.

Rimsky-Korsakov first worked on Sadko in 1867, but it was not then an opera, but rather a tone poem. Only in 1892, after he had revised this piece, did he decide to turn it into a dramatic work. Instead of traditional acts, Sadko is divided in seven tableaux, and, as that type of structure would suggest, is more loosely constructed than a traditional opera. The music is highly evocative, and Rimsky-Korsakov's famed gift of orchestration is abundantly in evidence throughout the score.