1951 National League tie-breaker series

The 1951 National League tie-breaker series was a best-of-three playoff series that extended Major League Baseball's (MLB) 1951 regular season to decide the winner of the National League (NL) pennant. The games were played on October 1, 2, and 3, 1951, between the New York Giants and Brooklyn Dodgers. It was necessary after both teams finished the season with identical win–loss records of 96–58. It is most famous for the walk-off home run hit by Bobby Thomson of the Giants in the deciding game, which has come to be known as baseball's "Shot Heard 'Round the World".

This was the second three-game playoff in NL history. After no tiebreakers had been needed since the American League (AL) became a major league in 1901, this was the third such tie in the previous six seasons. The Dodgers had been involved in the previous one as well, losing to the St. Louis Cardinals during the 1946 season in two straight games. In addition to the 1946 series, the AL had a one-game playoff in 1948.

The Giants won game one, while the Dodgers came back to win game two. After trailing for most of game three, the Giants rallied to win the game and the series. Consequently, they advanced to the 1951 World Series, in which they were defeated by the New York Yankees. In baseball statistics, the tie-breaker series counted as the 155th, 156th, and 157th regular season games by both teams; all events in the games were added to regular season statistics.