The Bityug (Russian: Битюг) is a river in Voronezh Oblast, Russia, a left tributary of the Don. Its upper reaches are located in Tambov Oblast. The Bityug is 379 kilometres (235 mi) long, with a basin of 8,840 square kilometres (3,410 sq mi). There are more than 400 lakes in the Bityug basin. The river freezes up in mid-December and stays icebound until late March or early April.