The Mayn River (Russian: Майн), sometimes spelled Main River, is a river in Chukotka Autonomous Okrug (Magadan Oblast) in Russia, one of the major tributaries of the Anadyr River. The length of the river is 475 kilometres (295 mi). The area of is drainage basin is 32,800 square kilometres (12,700 sq mi). It is a right tributary, flowing roughly northwards from its source in the small Mainskoe Lake, located in the northern part of the Parapol Valley, in the Koryak Mountain Range. This river passes then through sparsely populated areas of the forest-tundra subzones of Chukotka. The vegetation of the area includes mosses, lichens, dwarf shrubs, and sedge.
The Main River meets the Anadyr at Ust-Maynin the mid-lower stretch of its course, in an area of wetlands and small lakes, about 65 kilometres (40 mi) further upstream from the confluence of the Anadyr and the Belaya River. All these rivers are frozen for about eight to nine months in a year.
The whole basin of the Main River and its tributaries belong to the Chukotka Autonomous Okrug.
Latitude: 63° 30' N, Longitude: 171° 15' E
The chum salmon and the sockeye salmon are common in the waters of the Main River.
Vayegi town lies in the Main's middle course and Ust-Mayn village lies at the confluence of the Main and Anadyr Rivers.