A helmet, comprising: a helmet shell; a retention system (100, 220) attached to the helmet shell, the retention system comprising a rear portion (102, 222) connected to the rear of the helmet shell such that the rear portion is moveable relative to the helmet shell, a pair of side straps extending from the rear portion to right and left temple portions of the helmet shell, a pair of securing members (120, 420) attached to the right and left temple portions of the helmet shell, and an adjustment device (114, 232) attached to the rear portion and configured to selectively adjust the length of each of the pair of side straps between the rear portion and the right and left temple portions of the helmet shell; a chin portion configured to receive the chin of a person wearing the helmet; a pair of first chin straps extending from the chin portion to the rear portion, wherein the length of each first chin strap between the chin portion and the rear portion is selectively adjustable; and a pair of second chin straps extending from the chin portion to right and left temple portions of the helmet shell, wherein the length of each second chin strap between the chin portion and the temple portions of the helmet is selectively adjustable; wherein each of the pair of side straps comprises a strap segment (110, 450, 452) extending from the rear portion, and an elongated member (112, 240) movably attached to the strap segment and extending from the adjustment device to one of the securing members; and wherein the securing members movably attach the elongated members to the temple portions of the helmet shell; and wherein the adjustment device is configured to selectively adjust the elongated members to move the strap segments relative to the helmet shell and adjust the length of each of the pair of side straps between the rear portion and the temple portions of the helmet shell by changing a distance between the ends of the strap segments and the securing members; and wherein at least a portion of the pair of side straps are tightened against the right and left sides of the user's head and the rear portion is pulled forward and upward against the rear of the user's head when the elongated members of the side straps are retracted into the adjustment device. a helmet shell; a retention system (100, 220) attached to the helmet shell, the retention system comprising a rear portion (102, 222) connected to the rear of the helmet shell such that the rear portion is moveable relative to the helmet shell, a pair of side straps extending from the rear portion to right and left temple portions of the helmet shell, a pair of securing members (120, 420) attached to the right and left temple portions of the helmet shell, and an adjustment device (114, 232) attached to the rear portion and configured to selectively adjust the length of each of the pair of side straps between the rear portion and the right and left temple portions of the helmet shell; a chin portion configured to receive the chin of a person wearing the helmet; a pair of first chin straps extending from the chin portion to the rear portion, wherein the length of each first chin strap between the chin portion and the rear portion is selectively adjustable; and a pair of second chin straps extending from the chin portion to right and left temple portions of the helmet shell, wherein the length of each second chin strap between the chin portion and the temple portions of the helmet is selectively adjustable; wherein each of the pair of side straps comprises a strap segment (110, 450, 452) extending from the rear portion, and an elongated member (112, 240) movably attached to the strap segment and extending from the adjustment device to one of the securing members; and wherein the securing members movably attach the elongated members to the temple portions of the helmet shell; and wherein the adjustment device is configured to selectively adjust the elongated members to move the strap segments relative to the helmet shell and adjust the length of each of the pair of side straps between the rear portion and the temple portions of the helmet shell by changing a distance between the ends of the strap segments and the securing members; and wherein at least a portion of the pair of side straps are tightened against the right and left sides of the user's head and the rear portion is pulled forward and upward against the rear of the user's head when the elongated members of the side straps are retracted into the adjustment device.