Shizunai River (Shizunai-gawa) is a river in Shinhidaka, Hokkaidō, Japan. The Shizunai River drains from the Hidaka Mountains into the Pacific Ocean. The Shizunai River was known as Shibuchari and Shibechari. This name was derived from Shipe-ichan meaining a salmon spawning place in Ainu.
The Shizunai River flows generally southwest from its headwaters in the Hidaka mountains at the confluence of the Koikakushushibichari and Koibokushushibichari rivers. It flows into Lake Takami (Takami-ko), a reservoir created by the Takami Dam. Past the dam, the Shizunai river flows into Shizunai Flood Control Reservoir (Shizunai Chōseichi). Past the Shizunai Dam, the river encounters Futa Dam before leaving the mountains for the flood plain. The river flows past the outlying communities of Shizunai before entering the Pacific Ocean just northwest of Shizunai harbor.