Sai River may refer to:
Sai River (Gujarat), a river in Gujarat, India Sai River (Uttar Pradesh), a tributary of the River Gomti in Uttar Pradesh, India Sai River (Nagano), a tributary of Shinano River, the longest in Japan Sai River (Gifu), a river in Gifu Prefecture, Japan Sai River (Ishikawa), a river near Kanazawa in Ishikawa Prefecture, Japan Sâi, a tributary of the Danube in Romania Sai River (Thailand), a river that forms the border between Thailand and Burma