A footwear liner includes two sides connected at a front seam and a back seam by stitching, an inner bottom piece connected to the two sides along a bottom seam by stitching, and an outer bottom piece adhered to the inner bottom piece. Each side includes an outer layer, an inner layer, and an intermediate layer that is impermeable to water and permeable to vapor. The outer bottom piece includes an outer layer and an inner layer that is impermeable to water and permeable to vapor. The two sides and the inner bottom piece cooperate to form a partial enclosure with a toe portion, a heel portion, and an open top portion. In the preferred embodiment, the front and back seams are covered by a sealing tape to waterproof the seams, and the outer bottom piece overlaps and is adhered to portions of the sides adjacent the bottom seam to form a waterproof seal between the outer bottom piece and the sides.