The Hill Submachine Gun was a prototype submachine gun designed by John L. Hill, a Texan firearms designer.
The Hill SMG was designed in 1952. It was chambered for 9×19mm Parabellum ammunition, which was stored in a then-unique magazine system that was aligned and mounted on the top of the weapon. The magazine was transparent. The empty casings were ejected through the pistol grip. Ammunition for the magazines was pre-packed, since there was no magazine opening in the gun. Two models were made, one with a wooden grip and stock, and another with a plastic pistol grip and no stock. Because of its complexity, the weapon has never achieved any success beyond prototype stages. Its design, however, perhaps inspired the very similar FN P90 PDW.