William Roy (1726–1790) was a Scottish military engineer, surveyor, and antiquarian.
William Roy may also refer to:
- William R. Roy (1926–2014), United States Representative from Kansas
- Bill Roy Jr. (born 1954), American member of the Kansas state legislature and son of William R. Roy
- William Roy (medium) (1911–1977), notorious fraud medium in the history of British spiritualism
- William Burton Roy (born 1958), retired USAF officer and Olympian sport shooter