Lester Bowles ("Mike") Pearson (1897-1972) was Prime Minister of Canada from 1963 until 1968. He lead the Liberal Party to two minority victories in the elections of 1963 and 1965.
Pearson won the Nobel Peace Prize in 1957 for his work on forming the United Nations peacekeeping forces following the Suez crisis.
Pearson is responsible for some of the most important legislation passed by Parliament in the 20th century. His government brought in universal health care, and the Canada pension plan. It also adopted the new Canadian flag. Most of these reforms were supported in the House by the New Democratic Party under Tommy Douglas.1
1. Tommy Douglas was recently voted the The Greatest Canadian. Lester Pearson is #6 and his Minister of Justice, Pierre Trudeau, is #3.