Foldable composite structures and methods for fabricating foldable composite structures are provided. For example, a method comprises selectively applying a rigidifying substance to a sheet of composite material to define a plurality of hinges; allowing the rigidifying substance to cure; and folding the sheet of composite material along the hinges to form the composite structure. As another example, a method comprises laying out flat a sheet of composite material; masking a plurality of hinges on the sheet; applying a polymer to a sheet face; curing the polymer; removing the masking; and folding the sheet along the hinges to form the composite structure. An exemplary foldable composite structure comprises a planar sheet of composite material folded to define a plurality of surface segments and a plurality of hinges. A portion of the hinges form peaks and the remainder of the hinges form valleys. The hinges are defined between adjacent surface segments.