Archibald Paton Thornton (1921 – 19 February 2004) was an academic and historian. He was the author of the seminal history of the British Empire, The Imperial idea and its enemies: a study in British power (St. Martin's Press, 1959). He was professor of history at University College, University of Toronto. He was the author of West-India Policy under the Restoration (1956), The Imperial Idea and its Enemies (1959), Doctrines of Imperialism (1965), The Habit of Authority (1966), For the File on Empire (1968), and Imperialism in the 20th Century (1978).