The Nihonbashi River (日本橋川, Nihonbashi-gawa) is a river which flows through central Tokyo, Japan. It is a distributary river of the Kanda River and flows into the Sumida River near the Eitai Bridge. The river is 4.8 km (3.0 mi) in length and passes through Chiyoda and Chuo wards. The river was created by a re-channeling of the former Hira River in the 15th Century at the direction of Ōta Dōkan to form a part of the external fortifications and water management plan for Edo Castle.