The Shizunai River drains from the Hidaka Mountains into the Pacific Ocean.

This name was derived from Shipe-ichan, meaning "a salmon spawning place" in Ainu.

[2] The name Shizunai is derived from the Ainu language and has three possible sources:[3] The Shizunai River flows generally southwest from its headwaters in the Hidaka mountains at the confluence of the Koikakushushibichari and Koibokushushibichari rivers.

The Shizunai River was designated as a wildlife protection area in 1965.

[2] The Shizunai River basin was the home of the Ainu leader who led Shakushain's revolt against the Shogunate-era Yamato people, especially the Matsumae clan, in the 1660s.