Lester Bowles Pearson (23 April 1897 – 27 December 1972) was a Canadian politician, diplomat, and scholar who served as the 14th prime minister of Canada from 1963 to 1968. He also served as leader of the Liberal Party from 1958 to 1968 and as leader of the Official Opposition from 1958 to 1963.
Born in Newtonbrook, Ontario (now part of Toronto), Pearson pursued a career in the Department of External Affairs went on to serve as the Canadian ambassador to the United States from 1944 to 1946. He entered politics in 1948 as Secretary of State for External Affairs, serving in that position until 1957 in the governments of William Lyon Mackenzie King and Louis St. Laurent. Pearson was also the seventh president of the United Nations General Assembly from 1952 to 1953. He was a candidate to become secretary-general of the United Nations in 1953, but was vetoed by the Soviet Union. He later won the Nobel Peace Prize in 1957 for organizing the United Nations Emergency Force to resolve the Suez Crisis, for which he received worldwide attention. After the Liberal Party was defeated in the 1957 federal election, Pearson handily won the leadership of the party in 1958. He suffered two consecutive defeats by Progressive Conservative prime minister John Diefenbaker in 1958 and 1962. He successfully challenged Diefenbaker for a third time in the 1963 federal election, winning a minority government. Pearson's Liberals won another minority government in the 1965 federal election.