William Lyon Mackenzie King OM CMG PC (December 17, 1874 – July 22, 1950) was a Canadian statesman and politician who served as 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. King is best known for his leadership of Canada throughout the Great Depression and the Second World War. He played a major role in laying the foundations of the Canadian welfare state and established Canada's international reputation as a middle power fully committed to world order. With a total of 21 years and 154 days in office, he remains the longest-serving prime minister in Canadian history.