Abstract: A reversible envelope in which sealed, interior envelope spaces are formed from a front panel and from bottom and end panels attached to the front panel that are folded toward each other and attached to each other with a releasible glue and from a flap panel that is attached to the front panel along an integral flap-panel hinge and that comprises a proximal flap portion adjacent the flap-panel hinge and a distal flap portion attached to the proximal flap portion at an integral mid-flap hinge, wherein the flap panel further comprises a cut line connecting two interior points of the mid-flap hinge to form an interior flap panel attached to the proximal flap portion along the mid-flap hinge, wherein the interior flap panel is releasibly attachable to a first exterior envelope surface while the distal flap portion is folded into the interior of the first folded form of the envelope and the distal flap portion is attachable to a second exterior envelope surface after the interior flap panel is released and the env