The Kitakami River (北上川, Kitakami-gawa) is the fourth largest river in Japan and the largest in the Tōhoku region. It is 249 kilometres (155 mi) long and drains an area of 10,150 square kilometres (3,920 sq mi). It flows through mostly rural areas of Iwate and Miyagi Prefectures. The source of the river is the Mount Nanashiruge in northern Iwate, from which it flows to the south between the Kitakami Mountains and the Ou Mountains.