Abstract: A portable collapsible boat comprises a body formed of a bottom and a pair of sides which are integrally molded with the bottom. The sides are elastically flexible so as to be foldable to horizontal positions overlying the bottom, and unfoldable to upright positions. A bow support plate and a stern support plate can be inserted generally horizontally between upper portions of the sides to retain the sides in their unfolded state. The support plates are pivotably connected to the sides so as to be automatically lowered to positions inside of the boat when the sides are folded, and automatically raised to positions adjacent upper edges of the sides when the sides are unfolded.