The Agano River (Agano-gawa) is a river which flows from Fukushima Prefecture to Niigata Prefecture in Japan. It is called the Aga River or the Ōkawa River in Fukushima. It is 210km long with 7,710km² watershed.
The source of the river is Mount Arakai on the border of Fukushima and Tochigi. It flows to the north and meets the Nippashi River from Lake Inawashiro and the Tadami River in the Aizu Basin, and then turns to the west and falls into the Sea of Japan. Its river mouth flow is the largest of any river in Japan.