What is the longest river in Japan?

The Shinano River is 228 miles long, and hence the longest, and also the widest, river in Japan. The river rises from the Japanese Alps in Mount Kobushi, flows northwest to meet the Sai River from Matsumoto and drains into the Sea of Japan. The junction of Chikuma and Sai is famous as the historical site where the Kawanakajima Battles broke. The river provides water for irrigation schemes in Niigata rice plains. In fact, Shinano provides a port for this town.