William Lyon Mackenzie King

William Lyon Mackenzie King was the tenth prime minister of Canada for three non-consecutive terms from 1921 to 1926, 1926 to 1930, and 1935 to 1948. A Liberal, he was the dominant politician in Canada from the early 1920s to the late 1940s. With a total of 21 years and 154 days in office, he remains the longest-serving prime minister in Canadian history.