An ultrathin covered structural panel includes a panel body made from a relatively lightweight moldable material such as expanded polypropylene (EPP), expanded polystyrene (EPS), expanded polypropylene with added strengtheners (XPP), polystyrene/polyphenylene ether (GECET.RTM.) foam, polyurethane foam, polystyrene foam, fiberglass materials, glass fiber-reinforced polypropylene (Azdel.RTM. composites), or treated reclaimed cellulose. The structural panel also includes one or more rigid high-strength structural inserts in the interior of the panel body. The structural panel further includes a covering on at least one side of the panel body. The structural panel is not more than about 20 mm thick. In a method of making the structural panel, one or more rigid high-strength structural inserts are placed into the cavity of a mold. The mold cavity has the shape of the structural panel and has a thickness of not more than about 20 mm. The mold is closed. A relatively lightweight moldable material is introduced into the mold cavity so that the moldable material surrounds the insert(s) and fills the mold cavity. The moldable material is allowed to harden to form the structural panel, and the finished structural panel is removed from the mold.