Miass River (Миасс) is a river in the Chelyabinsk and Kurgan Oblasts in Russia. It is a right tributary of the Iset River of the Irtysh basin. The length of the river is 658 km. The area of its basin 21,800 km². The Miass River freezes up in late October-November and stays under the ice until April. The cities of Chelyabinsk and Miass are located on the Miass River.