William Parsons may refer to:
- William Parsons (composer and copyist) (fl.1545–1563), English Renaissance composer and copyist from Wells
- William Parsons (composer and musician) (1745/6–1817), Master of the King's Music
- William Parsons (poet) (died 1828), English writer associated with the Della Cruscan movement
- William Barclay Parsons (1859–1932), American civil engineer
- William E. Parsons (1872–1939), American architect and city planner
- William Sterling Parsons (1901–1953), American naval officer and atomic bomb weaponeer aboard Enola Gay
- William W. Parsons (academic administrator) (1850–1925), president of Indiana State Normal School, later known as Ball State University
- William W. Parsons (NASA), former director of the NASA John F. Kennedy Space Center, & Space Shuttle Program manager
- William Henry Parsons (New York activist) (died 1935), headed the New York Society for the Suppression of Vice
- William Henry Parsons (colonel) (1826–1907), American newspaper editor, legislator, and Confederate colonel
- William Parsons (actor) (1736–1795), British actor and painter
- William Parsons (silent film actor) (1878–1919), American silent comedy film actor often credited as "Smiling Bill Parsons"
- Bill Parsons (born 1948), baseball player
- Sir William Parsons, 1st Baronet of Langley (c.1636–c.1662), of the Parsons baronets
- Sir William Parsons, 1st Baronet of Bellamont (died 1650), Surveyor General of Ireland and Member of Parliament
- Sir William Parsons, 2nd Baronet of Bellamont (died 1658), Earl of Rosse
- Sir William Parsons, 2nd Baronet of Birr Castle (died 1741), Earl of Rosse
- Sir William Parsons, 4th Baronet of Birr Castle (1731–1791), Irish politician
- William Parsons, 3rd Earl of Rosse (1800–1867), Lord Rosse, Irish astronomer
- William Parsons, 5th Earl of Rosse (1873–1918), Irish peer and British Army officer
- William Parsons, 7th Earl of Rosse (born 1936), worked for the United Nations