| Waiau River | |
| Mouth Location: | Hikuwai River |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
Waiau River is a river in the Gisborne Region of New Zealand. It has its headwaters in the same area of hill country to the east of the Raukumara Range as the Mata River, flowing firstly north, then east to become a tributary of the Hikuwai River.