The Fair at Sorochyntsi is a comic opera in three acts by Modest Mussorgsky, composed between 1874 and 1880 in St. Petersburg, Russia. The composer wrote the libretto, which is based on Nikolay Gogol's short story of the same name, from his early (1832) collection of Ukrainian stories Evenings on a Farm near Dikanka. The opera remained unfinished and unperformed upon Mussorgsky's death in 1881.

Mussorgsky worked on the opera between 1874 and 1880, in competition with his work on Khovanshchina (1872–1880); both were incomplete at the time of his death in 1881. He reused some music that he had written previously (such as the "Market Scene" from Act II of the ill-fated Mlada of 1872, used for the opening scene of Fair). Incorporation of the music of Night on Bald Mountain as a dream sequence involving the hero was a late addition to the scenario in the course of composition, despite the fact that such an episode is not suggested by the original story. Although Mussorgsky managed to complete some numbers and even some of the orchestration, significant portions of the scenario were left without any music at all or only in bare sketches.

Several subsequent composers and editors (cited below) played partial or maximal roles in bringing the work into a performable state. The first staged performance, with spoken sections, occurred on 8 October 1913 in Moscow under Konstantin Saradzhev. Beginning in 1917, the first of several fully sung versions reached the stage.