Sergei Vladimirovich Protopopov (Russian: Серге́й Владимирович Протопопов; 2 April [O.S. 21 March] 1893, Moscow – 14 December 1954, Moscow) was a Russian avant-garde composer and music theorist.

After studying medicine at the Moscow University, he attended the Kiev Conservatory where he pursued studies of music with theorist Boleslav Yavorsky. He graduated in 1921 and started working as a conductor. During 1938–43, he taught at the Moscow University.

He was associated, as many composers of the Russian avant-garde, with the Association for Contemporary Music. Due to the ideological incompatibility of avant-garde with the contemporary regime supporting socialist realism, his works were mostly unknown following 1931.

Both in his compositions and in his teaching, Protopopov was a strong supporter of Yavorsky's theories of modal rhythm and tritone. He also maintained a close relationship with him. Protopopov's compositions include three piano sonatas and some vocal works with piano. The piano sonatas were strongly influenced by late Scriabin. Using simultaneously sounding semitones, he created a specific harmony. Technically, they are very demanding for the interpreter, as well as for the instrument—they employ full standard range of piano, sometimes going even beyond that. The piano sonatas are often notated in three staves, and for simplicity accidentals take effect only at the given note.

• Powell, Jonathan. "Protopopov, Sergey Vladimirovich", The New Grove Dictionary of Music and Musicians.
• Sitsky, Larry (1994). "24 Sergei V. Protopopov: The Post-Scriabin Composer". Music of the repressed Russian avant-garde, 1900–1929. Greenwood Publishing Group. pp. 283–290. ISBN 9780313267093. Retrieved 2010-07-23.

• Free scores by Sergei Protopopov at the International Music Score Library Project (IMSLP)
• Biography at All Music Guide
• The Musical Legacy of Sergei Protopopoff by Anton Rovner
• Protopopov at Last Fm