George McClellan Sebree III (August 26, 1932 – March 7, 2010), better known as Mac Sebree, was an American journalist, writer and publisher whose area of expertise was urban mass transit, particularly urban rail transit. He was also a businessman, being owner and president of the publishing company, Interurban Press, from 1975 until 1993. In addition to writing and publishing historical material, he also followed – and regularly reported on – contemporary developments concerning rail transit, and by the 1990s he had become an expert on light rail in North America.
G. M. Sebree adopted the nickname "Mac" at an early age and went by the name Mac Sebree, both personally and professionally, for most of his life, only modifying this slightly in 1995, to G. Mac Sebree. Growing up in Omaha, Nebraska, he later lived in Albuquerque, New Mexico, and attended the University of New Mexico. He was editor of the university's student newspaper (at the time named the New Mexico Lobo) from June to September 1954. Later, he was employed as a reporter for an Albuquerque newspaper. He worked as a newspaperman from 1956 until 1982, including 20 years covering transportation for United Press International (UPI) and the Scripps newspapers, the UPI stint lasting 11 years. For several years he additionally worked as a salesman for a syndicated service providing illustrations for newspaper advertisements, the Stamps-Conhaim Creative Newspaper Advertising Service. He moved from Albuquerque to Southern California in the late 1960s.