The Ōpārau River is a river of the Waikato Region of New Zealand's North Island in the area occupied by Ngāti Hikairo. It flows southwest from its sources in the Pirongia Forest Park, the highest being The Cone, and flows into the Kawhia Harbour, 5 kilometres (3 mi) east of Kawhia. The river has about 171 km (106 mi) of tributaries.