is a river in Hokkaido, Japan. Located in Kamikawa and Iburi subprefectures, it is one of 13 major 'class 1' rivers on the island. Course The Mu River rises on the slopes of Mount Karifuri in the Hidaka Mountains. It flows south and west until it reaches the Pacific Ocean at Mukawa. Dams Tributaries Shimukappu (upper reaches): Horoka Tomamu River Soshubetsu River Pankeshuru River Shimu River Mukawa (lower reaches): Ososukenai River Tosano River Horosaru River Hobetsu River Rubeshibe River Kinausu River Inaeppusawa River Niwan River Yunosawa River Chin River References Rivers of Hokkaido