Major-General William Roy FRS, AS (1726–1790) was a Scottish military engineer, surveyor, and antiquarian. He was an innovator who applied new scientific discoveries and newly emerging technologies to the accurate geodetic mapping of Great Britain.It was Roy's advocacy and leadership that led to the creation of the Ordnance Survey in 1791, the year after his death. His technical work in the establishment of a surveying baseline won him the Copley Medal in 1785.