The Minor Leagues of baseball are a professional league competing a level below the Major Leagues. They are operated as independent businesses, but the best known leagues are members of Minor League Baseball, the main organization that has agreements with the Major Leagues to operate as their affiliates. The purpose of this affiliation is to develop players that will be available to the Major Leagues upon demand.

There are twenty minor baseball leagues in operation with 246 member clubs in many towns across the United States and Canada. The Major Leagues have a 40 Man Roster; however, only 25 of those men actually play for the major league club, while the remaining 15 players usually play in the Triple-A level of the minor leagues (or may be on the disabled list). This arrangement means that the 15 players not regularly played in the majors have the opportunity to play daily and stay up to par rather than spending the season on the bench. Any minor league players that are not on the 40 Man Roster are under contract to the parent major league club, but they do not have a union. They work for a much lower salary and play somewhere between Rookie and Triple-A minor league levels.