Marvin Julian Miller was an American labor union leader and baseball executive who served as the executive director of the Major League Baseball Players Association (MLBPA) from 1966 to 1982. Miller led MLBPA during three strikes and two lockouts. Under Miller's direction, the players' union was transformed into one of the strongest unions in the United States.

The Major League Baseball Players Association (MLBPA) is the labor union representing all current Major League Baseball players. All players, managers, coaches, and athletic trainers who hold or have held a signed contract with a Major League club are eligible for membership in the Association.