An adaptive fit helmet, comprising: an outer shell; an energy-absorbing material disposed within the outer shell; a fit system coupled to the outer shell; characterized in that the outer shell comprises: a top portion which extends from the top of the helmet to the lower exterior edge of the outer shell such that the top portion also includes a rear tapered interface portion to cover a rear portion of the user's head, including the occipital curve of the user's head, when helmet is worn by the user; a side portion which is formed in a U-shape that can be disposed over the forehead and side portions of the user's head while creating an opening in a center of the U-shape that is configured to receive the top portion,wherein the top portion and side portion of the outer shell interface along the U-shape when placed together; and an outer expansion area that extends along an interface between the top portion and the side portion of the outer shell, from a temple area of the outer shell, to the lower exterior edge of the outer shell; and wherein the fit system comprises a belt coupled to the side portion of the outer shell and a fit system mechanism coupled to the top portion of the outer shell and the belt, wherein a position of the fit system controls a three-dimensional size and shape of the outer shell. an outer shell; an energy-absorbing material disposed within the outer shell; a fit system coupled to the outer shell; characterized in that the outer shell comprises: a top portion which extends from the top of the helmet to the lower exterior edge of the outer shell such that the top portion also includes a rear tapered interface portion to cover a rear portion of the user's head, including the occipital curve of the user's head, when helmet is worn by the user; a side portion which is formed in a U-shape that can be disposed over the forehead and side portions of the user's head while creating an opening in a center of the U-shape that is configured to receive the top portion,wherein the top portion and side portion of the outer shell interface along the U-shape when placed together; and an outer expansion area that extends along an interface between the top portion and the side portion of the outer shell, from a temple area of the outer shell, to the lower exterior edge of the outer shell; and a top portion which extends from the top of the helmet to the lower exterior edge of the outer shell such that the top portion also includes a rear tapered interface portion to cover a rear portion of the user's head, including the occipital curve of the user's head, when helmet is worn by the user; a side portion which is formed in a U-shape that can be disposed over the forehead and side portions of the user's head while creating an opening in a center of the U-shape that is configured to receive the top portion,wherein the top portion and side portion of the outer shell interface along the U-shape when placed together; and an outer expansion area that extends along an interface between the top portion and the side portion of the outer shell, from a temple area of the outer shell, to the lower exterior edge of the outer shell; and wherein the fit system comprises a belt coupled to the side portion of the outer shell and a fit system mechanism coupled to the top portion of the outer shell and the belt, wherein a position of the fit system controls a three-dimensional size and shape of the outer shell.