152 mm mortar M1931 (NM) (Russian: 152-мм мортира образца 1931 года (НМ)) was a 152.4 mm (6 inch) artillery piece originally developed by the German arms manufacturer Rheinmetall. The gun was produced in limited numbers in the Soviet Union and saw action with the Soviet Army in World War II. A modified version of the design was also adopted in Germany, as 15 cm sIG 33.