William Mundy, or William Munday (c. 1529–1591) was an English composer of sacred music. He was the father of John Munday, organist and composer. Little is known about his life, except that he was appointed to the Chapel Royal in 1562–1563, and was replaced in 1591, presumably following his death. Some of his best-known choral works are Adolescentulus sum ego, a setting based on Psalm 118, Vox Patris caelestis, with words by William Forrest, and Infelix ego, which uses the text of a meditation on the Miserere, Psalm 51, composed in prison by Girolamo Savonarola.