Protva River ({{Lang-ru|Протва}}) is a river in Moscow and Kaluga Oblasts in Russia, left tributary of the Oka. The length of the river is {{convert|282|km}}. The area of its basin is {{convert|4620|km2}}. The Protva freezes up in early December and stays icebound until early April. Its main tributary is the Luzha River. The towns of Vereya, Borovsk, Protvino and Obninsk are located on the shores of the Protva River.