Prince Igor (Russian: Князь Игорь, romanized: Knyaz Igor, ) is an opera in four acts with a prologue, written and composed by Alexander Borodin. The composer adapted the libretto from the early Russian epic The Lay of Igor's Host, which recounts the campaign of the 12th-century prince Igor Svyatoslavich against the invading Cuman ("Polovtsian") tribes in 1185. He also incorporated material drawn from two medieval Kievan chronicles. The opera was left unfinished upon the composer's death in 1887 and was edited and completed by Nikolai Rimsky-Korsakov and Alexander Glazunov. It was first performed in St. Petersburg, Russia, in 1890.