The 1981 Mason-Dixon 500 was a NASCAR Winston Cup Series racing event that took place on May 17, 1981, at Dover Downs International Speedway (now Dover International Speedway) in the American city of Dover, Delaware. During the preceding season, NASCAR had completely stopped tracking the year model of all the vehicles and most teams did not take stock cars to the track under their own power anymore. Only manual transmission vehicles were allowed to participate in this race; a policy that NASCAR has retained to the present day.