The Negro leagues were professional baseball leagues primarily in the United States comprising teams of African Americans. The term may be used broadly to include professional black teams outside the leagues and it may be used narrowly for the seven relatively successful leagues beginning in 1920 that are sometimes termed "Negro Major Leagues".
In the late 19th century, the baseball color line developed, excluding African Americans from play in major baseball leagues and affiliated minor leagues (collectively known as organized baseball). The first professional baseball league consisting of all-black teams, the National Colored Base Ball League, was organized strictly as a minor league but failed in 1887 after only two weeks owing to low attendance.