The Tikhvinka is a river in Boksitogorsky and Tikhvinsky Districts of Leningrad Oblast, Russia, a right and the biggest tributary of the Syas. The town of Tikhvin is located on its banks. It is 144 kilometres (89 mi) long, and the area of its basin 2,140 square kilometres (830 sq mi). The main tributaries of the Tikhvinka are the Ryadan (left) and the Shomushka (right).