The Berezayka (Russian: Березайка) is a river in Valdaysky District of Novgorod Oblast and Bologovsky District of Tver Oblast of Russia. It is left tributary of the Msta River and belongs to the drainage basin of the Neva and the Baltic Sea. It is 150 kilometres (93 mi) long, and the area of its drainage basin is 3,230 square kilometres (1,250 sq mi). The principal tributary of the Berezayka is the Valdayka River (left).