Mitrofan Petrovich Belyayev (Russian: Митрофа́н Петро́вич Беля́ев; old style 10/22 February 1836, St. Petersburg – 22 December 1903/ 4 January 1904) was an Imperial Russian music publisher, outstanding philanthropist, and the owner of a large wood dealership enterprise in Russia. He was also the founder of the Belyayev circle, a society of musicians in Russia whose members included Nikolai Rimsky-Korsakov, Alexander Glazunov and Anatoly Lyadov. His surname is often transliterated as Belaieff or Belayev. In 1886 the important Russian painter Ilya Repin made a portrait of Belyayev.
Belyayev was the son of a rich Russian wood dealer and large land owner and of a Swedish mother. Early on, he was established as a successful buyer in his father's company, whose line he took over after 30 years. His passion, at first private, was however for music.
Belyayev had learned and played violin, viola and piano when in school, and played viola for many years in a string quartet. Later he became a member in a circle of friends in St. Petersburg of chamber musicians, and with the leaders of that time - Anatoly Lyadov and Alexander Borodin - undertook journeys in Russia and abroad to learn more music, among other places to Bayreuth. Belyayev learned several foreign languages, including German.
An important event for Belyayev's future and his important role as leader in Russian music life was his meeting in 1882 with the highly talented, scarcely 17-year-old Alexander Glazunov, whose 1st Symphony was premiered at that time. Belyayev's increasing commitment to the promotion of Russian composers led to a gradual retreat from his activity as a wood dealer. In 1884 he became founder of the "Glinka prize", which was awarded annually. In the first years the winners included Borodin, Mily Balakirev, Pyotr Ilyich Tchaikovsky, Nikolai Rimsky-Korsakov, César Cui and Lyadov.