Johann Wilhelm Hässler (March 29, 1747 – March 22 (other sources, March 29), 1822), was a German composer, organist and pianist.Hässler was born in Erfurt. He first studied under his uncle Johann Christian Kittel, who was an organist at Erfurt. His first post was as organist of the local Barfüßerkirche in around 1762. His father died in 1769 and from then on he also managed the family fur business, though he still managed concert tours of Germany in the early 1770s, then in other places in Europe in the 1780s and 1790s. On 15 April 1789 he entered an organ competition with Wolfgang Amadeus Mozart in Dresden during Mozart's Berlin journey. On these tours he also came into contact with Johann Nikolaus Forkel, Johann Adam Hiller, Franz Benda, and Carl Philipp Emanuel Bach. He spent 1790 to 1792 in London and then moved to Saint Petersburg before settling in Moscow in 1794, where he worked as a prominent music teacher and composer. He remained there until his death.