The 1913 major league baseball season began on April 9, 1913. The regular season ended on October 5, with the New York Giants and Philadelphia Athletics as the regular season champions of the National League and American League, respectively. The postseason began with Game 1 of the tenth World Series on October 7 and ended with Game 5 on October 11. In the third iteration of this World Series matchup, the Athletics defeated the Giants, four games to one, capturing their third championship in franchise history, since their previous in 1911.
The 1913 schedule consisted of 154 games for all teams in the American League and National League, each of which had eight teams. Each team was scheduled to play 22 games against the other seven teams of their respective league. This continued the format put in place for the 1904 season. This format would last until 1919.
National League Opening Day took place on April 9 with a game between the Philadelphia Phillies and Brooklyn Dodgers, while American League Opening Day took place the following day, with all AL teams but the Chicago White Sox and Cleveland Naps, playing. The final day of the regular season was on October 5. The World Series took place between October 7 and October 11.