The Selenga (Mongolian Сэлэнгэ in , Russian Селенга́ in ) is a river of Mongolia and Russia. Born in the Mounts from Khangaï under the name of Ider , it takes its name after its junction with the Muran . It then receives the Orkhon on its Right Bank and is thrown in the Lac Baïkal by a Delta of 546 km ². Its overall length is of 1  470 km, including 452 km under the name of Ider. It is navigable from April at November until Sukhe-Bator.