Colin Stanley Gum (1924 – 29 April 1960) was an Australian astronomer who catalogued emission nebulae in the southern sky at the Mount Stromlo Observatory using wide field photography. Gum published his findings in 1955 in a study entitled A study of diffuse southern H-alpha nebulae which presented a catalog, now known as the Gum catalog, of 85 nebulae or nebular complexes. Gum 12, a huge area of nebulosity in the direction of the constellations Puppis and Vela, was later named the Gum Nebula in his honour. Gum was part of the team, whose number included Frank John Kerr and Gart Westerhout, that determined the precise position of the neutral hydrogen plane in space.
Gum was appointed Head of the Observational Optical Astronomy programme at the University of Sydney in 1959. He died in a skiing accident at Zermatt, Switzerland the following year.
The crater Gum on the Moon is named after him. An obituary article on Gum appears in the Australian Journal of Science (Vol. 23, no. 4, 1960).
Gum was the brother-in-law of prominent academic Fay Gale, and was uncle to businessman Michael Gale.