Which is the longest and widest river in Japan?

The Shinano River, known as the Chikuma River in its upper reaches, is the longest and widest river in Japan and the third largest by basin area (behind the Tone River and Ishikari River). It is located in northeastern Honshu, rising in the Japanese Alps and flowing generally northeast through Nagano and Niigata Prefectures before emptying into the Sea of Japan.

The Shinano basin supports a large range of plant life, including over 1,100 species of plant which grow on the river bank, in the river bed or more broadly. The basin also supports a large range of animal life both in and around the river.