Lake Teletskoye (Altyn-Kyol) is the largest lake in the Altai mountain system and the Altai Republic, Russia.
Situated at the height of 434 m above sea level, the lake stretches like an 78 km long and 5 km wide strip between the mountain ridges Korbu and Al-tyntu. Its width area is 233 km², however, due to its considerable depth (325 m), the lake contains no less than 40 km³ of fresh water.
About 70 rivers and 150 temporary streams flow into the lake, the largest of them Tchulyshman River, supplying more than a half of the whole water. The lake is drained through the single outlet, the Biya River, which, after its confluence with Katun River, forms one of Siberia's largest rivers, the Ob River.