The 2S31 Vena () is a Russian self-propelled 120 mm mortar/cannon. "2S31" is its GRAU designation. The 2S31 is a 120 mm 2A80 120mm mortar/cannon mounted on the chassis of a BMP-3 infantry combat vehicle. It was developed by Joint Stock Venture "Plants of Motovilikha" (). The weapon system is equipped with digital automated fire control system, navigation system, and optical/electronic reconnaissance and target acquisition system. Mortar mines (up to 7.2 km range) and cannon shells (up to 13 km range) can be used, including guided, HEAT, smoke, and thermobaric munitions. The mass of the system is 19.5 tons.