Sim River (Russian: Сим) is a river in Chelyabinsk Oblast and the Republic of Bashkortostan in Russia. It is a tributary of the Belaya River, part of the Volga watershed. Its length is 239 kilometers (149 mi).The river has its sources in the southern Ural Mountains. It first flows in a north-northwesterly direction towards the towns of Sim and Minyar, before turning towards the west and then southwest.