William Lyon Mackenzie King, Canadian economist and politician, 10th Prime Minister of Canada (b. 1874)
William Lyon Mackenzie King (December 17, 1874 – July 22, 1950) was a Canadian statesman and politician who served as the 10th 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. Trained in law and social work, 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.

Born in Berlin, Ontario (now Kitchener), King studied law and the political economy in the 1890s and became concerned with issues of social welfare. He later obtained a PhD – the only Canadian prime minister to have done so. In 1900, he became deputy minister of the Canadian government's new Department of Labour. He entered the House of Commons in 1908 before becoming the federal minister of labour in 1909, serving under Prime Minister Wilfrid Laurier. After losing his seat in the 1911 federal election, King worked for the Rockefeller Foundation before briefly working as an industrial consultant. Following the death of Laurier in 1919, King acceded to the leadership of the Liberal Party and won a by-election to re-enter the Commons shortly after. Taking the helm of a party bitterly torn apart during the First World War due to the Conscription Crisis of 1917, he unified both the pro-conscription and anti-conscription factions of the party, leading it to victory in the 1921 federal election.

King established a post-World War I agenda that lowered wartime taxes, moderately reduced tariffs, and evolved the national capital, Ottawa. In the 1925 election, the Conservatives won a plurality of seats, but the Liberals negotiated a balance of power agreement with the agrarian Progressive Party. In 1926, facing a House of Commons vote that could force his minority government to resign, King unsuccessfully requested to dissolve parliament and call an election. This event triggered a major constitutional crisis. The Conservatives were invited by the governor general to form government, but lost a motion of no confidence, triggering an election in which the Liberals decisively won. After this, King sought to make Canada's foreign policy more independent by expanding the Department of External Affairs while recruiting more Canadian diplomats. His government also introduced old-age pensions based on need and removed taxes on cables, telegrams, and railway and steamship tickets. King's slow reaction to the Great Depression led to a defeat at the polls in 1930 at the hands of the Conservatives.

The Conservative government's response to the depression was heavily unpopular, and thus, King returned to power in a landslide victory in the 1935 election. Soon after, the economy was on an upswing. King negotiated the 1935 Reciprocal Trade Agreement with the United States, passed the 1938 National Housing Act to improve housing affordability, introduced unemployment insurance in 1940, and in 1944, introduced family allowances – Canada's first universal welfare program. The government also established Trans-Canada Air Lines (the precursor to Air Canada) and the National Film Board of Canada. Only days after the Second World War broke out, Canadian troops were deployed. The Liberals' overwhelming triumph in the 1940 election allowed King to continue leading Canada through the war. He mobilized Canadian money, supplies, and volunteers to support Britain while boosting the economy and maintaining morale on the home front. In order to satisfy French Canadians, King delayed introducing overseas conscription until late 1944. Even when the policy was introduced, he prevented an uprising in Quebec and a repeat of the 1917 national unity crisis with the assistance of his cabinet ministers Ernest Lapointe and Louis St. Laurent. The Allies' victory in 1945 allowed King to call a post-war election, in which the Liberals lost their majority government. In his final years in office, King and his government partnered Canada with other Western nations to take part in the deepening Cold War, introduced Canadian citizenship, and successfully negotiated Newfoundland's entry into Confederation. A modernizing technocrat, he wanted his Liberal Party to represent liberal corporatism to create social harmony.After leading his party for 29 years, and leading the country for 21 and a half years, King retired from politics in late 1948. He died of pneumonia in mid-1950. King's personality was complex; biographers agree on the personal characteristics that made him distinctive. He lacked the charisma of such contemporaries as Franklin D. Roosevelt, Winston Churchill, or Charles de Gaulle. Cold and tactless in human relations, he lacked oratorical skill and his personality did not resonate with the electorate. He had many political allies but very few close personal friends. He kept secret his beliefs in spiritualism and use of mediums to stay in contact with departed associates and particularly with his mother, and allowed his intense spirituality to distort his understanding of Adolf Hitler throughout the late 1930s. Historian Jack Granatstein notes, "the scholars expressed little admiration for King the man but offered unbounded admiration for his political skills and attention to Canadian unity." King is ranked among the top three of Canadian prime ministers.