The Pipeline Debate (May 8 – June 6, 1956) was a political event in the history of the Parliament of Canada. The debate was on the finances of the TransCanada pipeline, proper parliamentary procedure, and American economic influence on Canada. The controversy eventually contributed to the defeat of Louis St. Laurent at the polls in 1957, ending many years of Liberal rule, and bringing in a government under Progressive Conservative Prime Minister John Diefenbaker.