German Baroque composer and violinist, born in Dresden. He was also something of a prodigious linguist as well: from 1671 on he taught the Saxon princes Johann George and Friedrich August "in linguis exoticis", later becoming a chamber musician at the court. He was widely traveled: in 1680 he was enlisted as a cadet in a military campaign against the Turks, traveled to France and Italy in 1681, and in 1682 played before Louis XIV, already being considered one of the greatest violin virtuosos of his time. He ranked with Heinrich Ignaz Franz Biber and Johann Gottfried Walther among the most prominent violinists in German-speaking Europe. Subsequent journeys took Westhoff to Hungary, Italy, France, the Dutch Republic, and the imperial court in Vienna. Later, he became a professor of foreign languages at Wittenberg before in 1698 becoming a secretary to the Court of Saxony in Weimar, where he was a member of the court at the same time as Johann Sebastian Bach. The Sonatas for Violin without Bass that Westhoff wrote in 1696 were important forerunners for Bach's celebrated Sonatas and Partitas for Solo Violin written only 24 years later. Westhoff died in April 1705 in Weimar.
Westhoff's style was influenced by that of the somewhat older Walther, with whom he worked for several years in the Dresden court chapel.