William Gregg
William Gregg may refer to:
- William Gregg (VC), British First World War Victoria Cross recipient
- William Gregg (industrialist), founder of the pioneer Graniteville, South Carolina textile mill
- William Gregg (tennis), Australian tennis player in 1907 Australasian Championships
- William Gregg (New Zealand businessman), founder of the New Zealand company Gregg's
- William Gregg (clerk and spy), Scottish clerk and spy
- Bill Gregg, Australian rules footballer
- William O. Gregg, American bishop
- William Gregg (theologian), Canadian theologian and clergyman; Professor of Apologetics