Don Sinclair Davis, Ph.D. was an American character actor, theatre professor, painter and captain in the United States Army.
He was perhaps best known for playing General George S. Hammond in the science fiction television series Stargate SG-1 (1997–2007), and earlier for playing Major Garland Briggs on the television series Twin Peaks (1990–91). In the TV show MacGyver, he was the stunt/photography double for Dana Elcar. He was often mistaken for Elcar, and vice-versa. Davis did appear in two episodes of MacGyver, as a different character each time. His first appearance was as a cement truck driver in the episode "Blow Out", and his second appearance was as the poacher Wyatt Porter in "The Endangered". He also played Dana Scully's father in the series The X-Files. Canadian audiences may also be familiar with Davis thanks to his appearance in one of the famous Heritage Minutes, in which he played an arrogant American gold prospector who pulls a gun on Mountie Sam Steele. He also played the role of the Racine Belles' manager in the movie A League of Their Own. He also had a guest starring role in the pilot episode of the comedy-drama television series Psych, playing the character of Mr. McCallum.
Davis appeared in the 2017 series of Twin Peaks by the use of archive footage.