Mefistofele is an Italian opera in a prologue and five acts, later reduced to four acts and an epilogue, the only completed opera with music by the Italian composer-librettist Arrigo Boito. It is an adaptation of the German legend of Faust. The opera was given its premiere on 5 March 1868 at La Scala, Milan, under the baton of the composer, despite his lack of experience and skill as a conductor.