a river in the Mongolian People’s Republic, a right tributary of the Selenga River. It measures 1,124 km long and drains an area of 132,800 sq km.
The Orkhon originates in the Khangai Range. Its valley in the upper course is narrow, in places canyon-like; here the river has a waterfall approximately 20 m high. The middle Orkhon meanders through a deep valley. After emerging from the mountains, the river widens to 100–150 m. The mean flow rate near the mouth is approximately 120 cu m per sec. In spring there is high water from melting seasonal snow; in summer there are flash floods. The Orkhon is frozen from November through April. It is navigable as far as the city of Sukhe-Bator, and during high water as far as the mouth of the Tola River. Timber is floated on the Orkhon.