William Duncombe (ca. 1736-1738 30 November 1818, or 1819) was an English composer. He was organist in Kensington.
He is mainly known by a few small piano pieces (especially a Sonatina in C Major and the Fanfare or Fanfare Minuet) that are still reprinted in pedagogical collections. They are probably excerpts of the Progressive lessons for the harpsichord and piano forte, published in 1778 (or 1785).
Duncombe is frequently confused with the writer William Duncombe (1690 1769).