The Standschütze Hellriegel 1915 is a water-cooled submachine gun produced in very limited numbers for the Austro-Hungarian reserves (Standschütze) during World War I, by a designer identified only as "Hellriegel". A highly obscure weapon, no complete examples are known to still exist, and little official documentation remains. As a result, its operating mechanisms, exact production numbers and development history are all based on speculation. However, photographic evidence exists of it in live-fire tests which are dated October 1915, making it one of the earliest submachine gun designs in history.