| Waiau River | |
| Pushpin Map: | New Zealand#New Zealand North Island |
| Pushpin Map Size: | 270px |
| Pushpin Map Caption: | Mouth of the Waiau River |
| Source1: | Confluence of the Wairoa Stream and Parahaki Stream |
| Source1 Coordinates: | -38.7405°N 176.8526°W |
| Mouth Coordinates: | -38.9661°N 177.3967°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Progression: | Waiau River → Wairoa River → Hawke Bay → Pacific Ocean |
| Tributaries Left: | Te Waiotukapiti Stream, Manganuiohou River, Mangatoatoa Stream, Matuku Stream, Mangatoto Stream, Mangaone Stream, Waihi Stream, Mangapouri Stream, Raeuhoi Stream, Mangamauka Stream, Te Iringaowhare Stream, Waikaretāheke River |
| Tributaries Right: | Mangangarara Stream, Mangakahika Stream, Tatua Stream, Mangakahakaha Stream, Mangahopai Stream, Pukematai Stream, Pakihiwi Stream, Mangapirita Stream, Mangarangiora Stream, Owhio Stream, Mangawhero Stream, Tutaekuri River |
Hawke's Bay's Waiau River is one of at least four rivers of this name in New Zealand. It rises in the Kaingaroa Forest to the west of Lake Waikaremoana, and flows southeast for 60 kilometres before joining the Wairoa River.