The Tes River is a river in northwestern Mongolia and southern Tuva, Russia. Its spring is in Tsagaan-Uul sum in Khövsgöl. The river then flows through Zavkhan (Mongolia), Tuva (Russia), next back to Uvs (Mongolia) before entering Uvs Lake. While in Khövsgöl, there is a wooden bridge near Tsetserleg and a concrete bridge near Bayantes on the road to Kyzyl, Russia. The Tes River is primary source of the Uvs Lake. A large section of the river, from where it enters the Uvs Province to its mound in the lake, is included in the Uvs Nuur Basin UNESCO World Heritage Site.