Duncan McGregor (August 12, 1836 – May 30, 1921) was an American politician and educator.

Born in Perthshire, Scotland, McGregor emigrated with his father's family to the United States in 1856 and settled in Wisconsin.^[1] He had gone to Perth Academy and University of Aberdeen in Scotland and Lawrence University in Appleton, Wisconsin.^[1] McGregor farmed and was a teacher and principal of the Waupaca, Wisconsin High School. McGregor served in the 42nd Wisconsin Volunteer Infantry Regiment during the American Civil War and was commissioned captain.^[1] McGregor was the mathematics professor of Platteville Normal School in Platteville, Wisconsin.^[1] He also served as the institute conductor and president of the Platteville Normal School.^[2] In 1905 and 1907, McGregor served in the Wisconsin State Assembly and was a Republican. He also served as private secretary to Wisconsin Governor Francis E. McGovern.^[3] McGregor died at his home in Platteville, Wisconsin, May 30, 1921.^[1][2][4]