Shimanto-gawa is the longest river in Shikoku.
Starting from the east slope of Irazu-yama Mountain which towers 1336 meters above sea level, the water runs through 318 tributaries including 35 main feeders. The river meanders widely through the south western area of Shikoku and runs through a gentle elevation finally reaching the Pacific Ocean at Shimoda,  Shimanto City.
The upper reaches of the stream includes the northern area of Tsuno Town and Yusuhara Town  and is rich in nature throughout the seasons with scenic views such as Shikoku  Karst, Tengu-kogen Highland, Shimanto Genryu Forest and Shimanto Headwaters House. In the lower reaches of the river there are also attractions including boat trips, Dragonfly Park and Sata Chinka Bridge.
The river has an abundance of aquatic life, and the local fishery preserves traditional fishing methods unique to the region.