Sir David Gill FRS (12 June 1843 – 24 January 1914) was a Scottish astronomer who is known for measuring astronomical distances, for astrophotography, and for geodesy. He spent much of his career in South Africa. He was born in Aberdeen and educated at Dollar Academy. He spent two years at Aberdeen University, where he was taught by James Clerk Maxwell,and then joined his father's clock-making business. It would seem that Gill's interests lay elsewhere since after a few years he sold the business, and then spent time equipping Lord Lindsay's private observatory at Dun Echt, Aberdeenshire. In 1874, Gill joined the expedition to Mauritius to observe the transit of Venus. Three years later he went to Ascension Island to observe a near approach of Mars and to calculate its distance.
Gill used the parallax of Mars to determine the distance to the Sun, and also measured distances to the stars. He perfected the use of the heliometer. He was Her Majesty's Astronomer at the Cape of Good Hope from 1879 to 1906. He was a pioneer in the use of astrophotography, making the first photograph of the Great Comet of 1882, and one of the early proponents of the Carte du Ciel project.