String Quartet No. 1 in C major (Szymanowski)

String Quartet No. 1 in C Major Op. 37 is a composition for string quartet by Karol Szymanowski. It was the first of the two string quartets composed by Szymanowski. The work is from 1917 during his middle period. It is notable for its third movement, which contains four key signatures in its written four parts. These include the cello with 0 flats or sharps; the viola with 3 flats; the violin 2 with 6 sharps; and the violin 1 with 3 sharps, exemplifying polytonality.

Dedicated to the French musicologist Henry Prunières, the work won the first prize in the Polish Ministry of Religious Denominations and Public Enlightenment's chamber music competition. Its first public performance was in Warsaw on 7 March 1924 played by the Warsaw Philharmonic Quartet.