Sir John Cunningham McLennan, Ph.D , FRS , FRSC , KBE (October 14, 1867 – October 9 1935) was a Canadian physicist. Born in Ingersoll, Ontario, the son of David McLennan and Barbara Cunningham, he was the director of the physics laboratory at the University of Toronto from 1906 until 1932. In 1926, he was awarded the Royal Society of Canada's Flavelle Medal.
