The Omolon River (Russian: Омолон) is the principal tributary of the Kolyma River in northeast Siberia. The length of the river is 1,150 kilometres (710 mi). The area of its basin is 118,600 square kilometres (45,800 sq mi). The Omolon River freezes up in October and stays under ice until late May through early June. The lower 600 kilometres (370 mi) are navigable.
It begins in the Magadan Oblast less than 100 kilometres (62 mi) from the Sea of Okhotsk, flows north, forms part of the border of Magdan and Chukotka, crosses Chukota, briefly enters the Sakha Republic and joins the Kolyma about 125 kilometres (78 mi) from the Arctic. Its basin is surrounded by: (west) branches of the Kolyma, (south) Penzhina River and others that flow south, (east) Anadyr River and (northeast) Bolshoy Anyuy River. The upper Omolon is subalpine in the highlands, the middle is boreal forest and the lower part tundra. There is a Zakaznik in Chukotka to protect the forests.