The Alatyr (Russian: Алатырь, IPA: [ɐˈɫatɨrʲ]) is a river in Mordovia, Russia, and it is the left tributary of the river Sura. It is 296 kilometres (184 mi) long, and has a drainage basin of 11,200 square kilometres (4,300 sq mi). The Alatyr freezes up in November and stays icebound until April. The towns of Ardatov and Alatyr (Erzya: Ратор, Rator), are located on the Alatyr River.