The 1951 Major League Baseball season opened on April 16 and finished on October 12, 1951. Teams from both leagues played a 154-game regular season schedule. At the end of the regular season, the National League pennant was still undecided resulting in a three game playoff between the New York Giants and the Brooklyn Dodgers. After splitting the first two games, the stage was set for a decisive third game, won in dramatic fashion on a walk-off homerun from the bat of Giant Bobby Thompson, one of the most famous moments in the history of baseball, commemorated as the "Shot Heard 'Round the World" and "The Miracle at Coogan's Bluff". The Giants lost the World Series to defending champion New York Yankees, who were in the midst of a 5-year World Series winning streak.
September 13 – The St. Louis Cardinals become the first team in Major League history to play two different teams on the same day. Due to a rained out game, the Cardinals are forced to play the New York Giants in an afternoon game prior to their scheduled night game against the Boston Braves.