Alatyr River (Russian: Алатырь) is a river in Mordovia in Russia, Sura's left tributary. The length of the river is 296 km. The area of its basin is 11,200 km². The Alatyr freezes up in November and stays icebound until April. The towns of Ardatov and Alatyr Mordvin name Rator Osh, are located on the Alatyr River.