William Guybon Atherstone (/ˈæθərstoʊn/; 1814–1898) was a medical practitioner, naturalist and geologist, one of the pioneers of South African geology and a member of the Cape Parliament.

William, a young man of wide interests and outstanding ability, received his first training at Dr James Rose Innes's academy in Uitenhage, being at first apprenticed to his father and then serving as Assistant-Surgeon in the Sixth Frontier War 1834–1835.

He carried out research in lung-sickness, horse-sickness and tick-borne fever and was in 1847 the first surgeon outside Europe and America to perform an amputation using an anaesthetic.

This operation, on 16 June 1847, was performed on the Albany Deputy Sheriff, Mr F Carlisle, and was completely successful.

He traveled widely in the eastern Cape, Namaqualand and the Transvaal, collecting minerals, fossils, plant specimens and seeds, sending material to Hooker at Kew.