Colin Riley McMillan (July 27, 1935 - July 24, 2003) was a former Assistant United States Secretary of Defense under President George H. W. Bush during the Gulf War. He was awaiting confirmation as United States Secretary of the Navy in 2003 when he died from an apparently self-inflicted gunshot wound in the head at his New Mexico ranch.
McMillan was the chairman and CEO of Permian Exploration Corporation, an oil exploration company, the chairman of the First Federal Savings Bank in Roswell, New Mexico, and the founder and CEO of McMillan Production Company. He was appointed in 2001 to be the chairman of the Sallie Mae Corporation by President George W. Bush.
McMillan earned his bachelor's degree from the University of North Carolina in 1957. He served in the United States Marine Corps from 1957–1960 and in the Marine Corps Reserve from 1960 - 1972.
McMillan served in the New Mexico House of Representatives from 1971 through 1982. He ran for the United States Senate in 1994 but lost to incumbent Democrat Jeff Bingaman. In 2000, McMillan was the New Mexico state chairman of George W. Bush's successful presidential campaign.
Colin McMillan was survived by his wife Kay and their four children and eight grandchildren.