Apparatus for the ventilation of a rotor hub of a wind energy plant, with a cup-shaped ventilation cap, which has a circumferential side wall and a base portion, wherein the side wall has at least one bore for draining water and the base portion has at least one bore for ventilation, a pipe-shaped connection piece, which has an air entrance opening which runs out into an interior space of the rotor hub, wherein the ventilation cap is arranged before the air entrance opening and the at least one bore for ventilation is arranged in the ventilation cap outside of the air entrance opening of the pipe-shaped connection piece such that the air entrance opening is covered up by the ventilation cap.