This article is the electoral history of William Lyon Mackenzie King, the tenth Prime Minister of Canada. A Liberal, he was Canada's longest-serving prime minister, with three separate terms as prime minister (1921–1926, 1926–1930 and 1935–1948), for a total of 21 years and 154 days. He defeated Prime Ministers Arthur Meighen and R.B. Bennett at different times, and was succeeded by Prime Minister Louis St. Laurent in 1948.
King was elected to the House of Commons of Canada twelve times (1908, 1909, 1919, 1921, 1922, 1926 (twice), 1930, 1935, 1940, and 1945).
He was elected leader of the Liberal Party of Canada in 1919, by the first leadership convention for a federal party in Canada.