The Onahau River is a river of the Tasman Region of New Zealand's South Island. It has its sources close to the northernmost point of Kahurangi National Park, from where it flows northeast to reach Golden Bay to the northwest of takaka. The smaller Little Onahau River follows a roughly parallel course to the southwest of the Onahau River.
"Place Name Detail: Onahau River". New Zealand Geographic Placenames Database. Land Information New Zealand. Retrieved 12 July 2009.
Coordinates: 40°48′S 172°46′E / 40.800°S 172.767°E