Ignaz Schuppanzigh (20 July 1776 – 2 March 1830) was an Austrian violinist, friend and teacher of Beethoven, and leader of Count Razumovsky's private string quartet. Schuppanzigh and his quartet premiered many of Beethoven's string quartets, and in particular, the late string quartets. The Razumovsky quartet, which Schuppanzigh founded in late 1808, is considered to be the first professional string quartet. Until the founding of this quartet, quartet music was played primarily by amateurs or by professional musicians who joined together on an ad hoc basis.
Schuppanzigh was born in Vienna, son of a professor of Italian at the Theresian Military Academy. After abandoning his early preferences for the viola, he established himself before his 21st birthday as a virtuoso violist and violinist, as well as a conductor. He gave violin lessons to Beethoven, and they remained friends until Beethoven's death.
Schuppanzigh's dedication to quartet playing played a pivotal role in the transition of quartet performance and composition. Prior to Beethoven, the quartet repertoire could be performed competently by good quality amateurs and by professionals with few rehearsals. Beethoven's quartets introduced many new technical difficulties that cannot be completely overcome without dedicated rehearsal. These difficulties include synchronized complex runs played by two or more instruments together, cross-rhythms and hemiolas, and difficult harmonies that require special attention to intonation. When Schuppanzigh complained to Beethoven about a particularly difficult passage, Beethoven is said to have remarked, "Do you believe that I think about your miserable fiddle when the muse strikes me?"
Razumovsky's quartet also premiered works by other composers. Franz Schubert dedicated his "Rosamunde" quartet to Schuppanzigh.
Schuppanzigh debuted a professional string quartet with audiences paying a subscription to hear concerts, the first of its kind.