Abstract: The protective storm window is a convex panel having a flat flange around the perimeter of the convex panel. The protective storm window is sized so that the flange may fit in to an existing frame of a window, door, vent or other opening in a building. The convex panel may be constructed out of fiberglass, plastic, metal or other suitable material depending on the intended use. Fixed and retractable pins are positioned along the outer edge of the flange to secure the protective storm window to an existing frame. One or more handles are attached to either the inside or outside of the flange to help a user install the protective storm window. The retractable pins may be spring-loaded and may be either individually operated or engage in unison through use of a sliding cam assembly. The protective storm window is stackable for easy storage.