Boris Godunov is an opera by Modest Mussorgsky (1839–1881). The work was composed between 1868 and 1873 in Saint Petersburg, Russia. It is Mussorgsky's only completed opera and is considered his masterpiece. Its subjects are the Russian ruler Boris Godunov, who reigned as Tsar during the Time of Troubles, and his nemesis, the False Dmitriy. The Russian-language libretto was written by the composer, and is based on the 1825 drama Boris Godunov by Aleksandr Pushkin, and, in the Revised Version of 1872, on Nikolay Karamzin's History of the Russian State.

Modest Petrovich Mussorgsky was a Russian composer, one of the group known as "The Five". He was an innovator of Russian music in the Romantic period. He strove to achieve a uniquely Russian musical identity, often in deliberate defiance of the established conventions of Western music.