Fyodor Serafimovich Druzhinin, also Fedor, (Russian: Фёдор Серафимович Дружинин; 6 April 1932 in Moscow – 1 July 2007) was a Soviet violist, composer and music teacher.
Druzhinin studied viola at the Moscow Central Music School with Nikolai Sokolov (1944–1950) and at the Moscow Conservatory with Vadim Borisovsky (1950–1957). In 1957, he won first place at the All-Union Competition of Musicians in Moscow. He replaced Borisovsky as violist of the Beethoven Quartet in 1964.
From 1980, Druzhinin was the head of the viola department at the Moscow Conservatory. Among his students are many noted violists such as Yuri Bashmet, Yuri Tkanov, Alexander Bobrovsky and Svetlana Stepchenko.
Druzhinin composed several works for viola. His Fantasia for Viola and Orchestra is best known. He worked closely with Dmitri Shostakovich and other composers such as Mieczysław Weinberg (Moisei Samuilovich Vainberg), Alfred Schnittke, Andrei Volkonsky, Roman Ledenyov. Shostakovich wrote his last composition for Druzhinin, the Sonata for Viola and Piano, Op.147 (1975). Other dedications include Concerto-Poem (1963–1964) for viola and orchestra by Ledenyov, Viola Sonata (1971) and Viola Concerto (1972) by Grigory Frid, and Weinberg's Sonata No.1 (1971) for unaccompanied viola.
Druzhinin was a 1988 recipient of the People's Artist of Russia award. In 2001, he published his memoirs: Воспоминания. Страницы жизни и творчества (Memoirs. Pages of Life and Work). The book relates countless memories of Shostakovich, Schnittke, Igor Stravinsky, Maria Yudina, Anna Akhmatova and colleagues of the Beethoven Quartet, among others.