1903 was the third year for the Detroit Tigers in the still-new American League. The team finished in fifth place with a record or 65–71 (.478), 25 games behind the Boston Americans. The 1903 Tigers outscored their opponents 567 to 539. The team's attendance at Bennett Park was 224,523, sixth out of the eight teams in the AL.

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.