The Wainui River is a river of the Tararua District in the Manawatū-Whanganui Region of New Zealand's North Island.

It rises on Mt McCartie and flows approximately 28 km (17 mi) southeast through isolated hill country to reach the Pacific coast at Herbertville, five kilometres west of Cape Turnagain.

[1] The name Wainui means large waters.

[2] The Wainui River has a number of small tributary streams.

This article about a river in Manawatū-Whanganui is a stub.