Captain William John Gill (10 September 1843 – 11 August 1882) was an English explorer and British army officer. He was born in Bangalore, India, the second child and elder son of the army officer, artist and photographer Major Robert Gill and his wife Frances Flowerdew Gill.

Major Robert Gill (1804–1879) was an army officer, antiquarian, painter and photographer in British India. He is best known for his paintings copying the frescoes of the Ajanta Caves. Gill was the first painter – after their rediscovery in 1819 – to make extensive copies of the Buddhist cave paintings, which mostly date to the 5th century CE. His surviving copies and drawings remain significant in Ajanta studies as the originals have significantly deteriorated since his time.