Johann Heinrich Schmelzer (c. 1620–1623 – between 29 February and 20 March 1680) was an Austrian composer and violinist of the middle Baroque era. Almost nothing is known about his early years, but he seems to have arrived in Vienna during the 1630s, and remained composer and musician at the Habsburg court for the rest of his life. He enjoyed a close relationship with Emperor Leopold I, was ennobled by him, and rose to the rank of Kapellmeister in 1679. He died during a plague epidemic only months after getting the position.
Schmelzer was one of the most important violinists of the period, and an important influence on later German and Austrian composers for violin. He made substantial contributions to the development of violin technique and promoted the use and development of sonata and suite forms in Austria and South Germany. He was the leading Austrian composer of his generation, and an influence on Heinrich Ignaz Biber.