Thomas Frederick Colby (1 September 1784 – 9 October 1852), was a British major-general and director of the Ordnance Survey (OS). A Fellow of the Royal Astronomical Society and Royal Society, Colby was one of the leading geographers of his time.An officer in the Royal Engineers, Colby overcame the loss of one hand in a shooting accident to begin in 1802 a lifelong connection with the Ordnance Survey. His most important work was the Survey of Ireland.