Tokoro River (常呂川) is a river in Hokkaidō, Japan. The Tokoro River, which has its source in Mt. Mikuni (alt. 1,541 m), flows through Oketo and Kunneppu towns and into the Sea of Okhotsk from Kitami City. Many white-tailed eagles and Steller’s sea eagles that have been designated as protected species by the national government are observed in its basin. A colony of purple azalea designated as a natural monument by the Hokkaido government and a forest of large-diameter Japanese elm trees along the Muka River, which flows parallel to the Tokoro River, are symbols of the region. At the Tokoro River Estuary Site, relics, remains of pit-dwellings and tomb pits from the Jomon era have been found.