Who Was Canada's Longest Serving Prime Minister?

Canada's longest serving prime minister was William Lyon Mackenzie King. King, of the Liberal Party, occupied the Prime Minister's Office for a total of 22 years. His first term lasted from 1921 to 1926 when he became the country's 10th prime minister. King led a minority government during these years and resigned in 1926 after the so-called King-Byng Affair.

King ran again in the 1926 elections and the Liberal Party won another minority, and thus formed the next government. King remained in power until 1930 when the Conservative Richard Bedford Bennett became Canada's next prime minister.

Mackenzie King made yet another comeback in 1935 when he won the election with a convincing lead over the Tories and was able to form a Liberal majority government.  King was then re-elected in 1940 and 1945. He remained prime minister until 1948.

Mackenzie King was best known for his cautious leadership style and centrist policies. Some critics, however, have also argued that he was not decisive enough and was unable to take a principled, firm stance on most issues. King's famous quote during World War II where he spoke of  "conscription if necessary, but not necessarily conscription." is often used to bolster this argument. He was, however, a strong voice for Canadian autonomy within the British Commonwealth.

Mackenzie King died in 1950.