A foldable electronic input device having a folded mode and an unfolded mode is provided. The foldable electronic input device includes a first body having a first surface and a second surface opposite to the first surface and a second body having a third surface. A first input area and a second input area are disposed on the first surface and the second surface, respectively. The third input area is disposed on the third surface. When in the folded mode, the second body is located directly below the first body and the third surface faces the second surface. When in the unfolded mode, the first body is located beside the second body, the second surface forms a plane with the third surface, and the second input area and the third input area constitute a fourth input area. A portable electronic device including the foldable electronic input device is also provided.