Duncan McArthur (March 17, 1885^[1][2] – July 20, 1943^[3]) was an archivist, educator, civil servant and political figure in Ontario. He represented Simcoe Centre from 1940 to 1943 in the Legislative Assembly of Ontario as a Liberal.^[4]

Born in Dutton, Ontario, McArthur was educated in Dutton, at Queen's University and at Osgoode Hall.^[3] He worked at the Dominion Archives of Canada from 1907 to 1912.^[5] In 1915, he was called to the Ontario bar and practised law in Toronto for two years. From 1919 to 1922, he was assistant general manager for a trust company. In 1920, McArthur married Floy Lawson.^[3] In 1922, he joined the history department at Queen's University, later serving as department head.^[1] In 1934, he became Ontario's Deputy Minister of Education.^[5]

McArthur was elected to the Ontario assembly by acclamation in 1940 following the death of Leonard Simpson.^[3] He served in the Ontario cabinet as Minister of Education from 1940 to 1943.^[4]

McArthur died of a heart attack at his summer home at Grand Bend on Lake Huron at the age of 58.^[3]

He was the author of several textbooks and contributed to the Cambridge History of the British Empire.^[3]

Duncan McArthur Hall at Queen's University, which houses the university's Faculty of Education, was named in his honour,^[1] as was Duncan McArthur Public School, also in Kingston (now closed).