The 50 cc class was the ultra-lightweight class in Grand Prix motorcycle racing, and formed part of the Fédération Internationale de Motocyclisme (FIM) World Championships from 1962 until 1983; when the class was replaced by 80 cc.

Grand Prix motorcycle racing is the highest class of motorcycle road racing events held on road circuits sanctioned by the Fédération Internationale de Motocyclisme (FIM). Independent motorcycle racing events have been held since the start of the twentieth century and large national events were often given the title Grand Prix. The foundation of the Fédération Internationale de Motocyclisme as the international governing body for motorcycle sport in 1949 provided the opportunity to coordinate rules and regulations in order that selected events could count towards official World Championships. It is the oldest established motorsport world championship.