The is a river in eastern Honshu, Japan. It flows through the prefectures of Tochigi and Ibaraki and empties to the Pacific Ocean. More than 50 species of fish live in the river, including dace, chum salmon, ayu, and herring. The Japanese government categorizes it as a Class 1 river. With a length of , the Naka drains an area of , including parts of neighboring Fukushima Prefecture. Its source is at Nasu-dake in Nikkō National Park.