Johann Wilhelm Hässler (1747-1822) was a German composer, pianist, and organist. He received his musical education from his uncle, Johann Christian Kittel, who was an organist at Erfurt. Hässler is known for his piano music, including sonatas, variations, and other works for the instrument, as well as his organ music and choral works. One of his most unusual compositions is a cycle of 360 preludes in all keys, Op. 47 (1817).
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.