The 1903 Philadelphia Athletics season was a season in American baseball. The team finished second in the American League with a record of 75 wins and 60 losses, 14½ games behind the Boston Americans.

The 1903 Boston Americans season was the third season for the professional baseball franchise that later became known as the Boston Red Sox. The Americans finished first in the American League (AL) with a record of 91 wins and 47 losses, 14+1⁄2 games ahead of the Philadelphia Athletics. Boston went on to participate in the first World Series held between the AL and National League (NL) champions. The Americans won the 1903 World Series in eight games over the Pittsburgh Pirates. The team was managed by Jimmy Collins and played its home games at Huntington Avenue Grounds.