An ultra-thin folding bristle hairbrush, capable of being operated with one hand, suitable for back-pocket storage. A base enclosure comprising a plurality of spaced transverse bristle bars, each bristle bar pivotally mounted within the base enclosure. At one end, the base enclosure is pivotally attached to a handle member. A kinematical linkage assembly adjoins the handle with the plurality of bristle bars whereby the opening and closing motion of the handle results in a synchronized articulation of the bristles from a stowed, generally horizontal, position, to a generally vertical position of use. The linkage lends itself to contouring the base enclosure and handle for ergonomic consideration such as back-pocket storage. The handle can also operate as a cover element. A unique one-handed “switchblade” action can be employed to flip open the brush, installing the bristles into their position of use.