Abstract: A helmet has a rigid head piece adapted to fit over a wearer's head and having a forwardly open cutout aligned with the wearer's face and a chin guard formed by a pair of generally identical right and left arms. Each arm is rigid and has a rear end juxtaposed with the respective side of the head piece and a front end. Mechanisms engaged between each rear end and the respective head-piece side can move the arms between a closed position with their front ends meeting underneath the face cutout and an open position with their front ends spaced apart and flanking the cutout. Latches on the front ends of the arms lock them together in the closed position.