| Waiau Uwha | |
| Map: | NZ-Waiau R (Canterbury).png |
| Map Size: | 270px |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Subdivision Type3: | Region |
| Subdivision Name3: | Canterbury |
| Subdivision Type4: | District |
| Subdivision Name4: | Hurunui |
| Subdivision Type5: | City |
| Subdivision Name5: | Hanmer Springs, Waiau, Parnassus |
| Source1: | Southern Alps |
| Source1 Location: | Spenser Mountains, New Zealand |
| Source1 Coordinates: | -42.1108°N 172.645°W |
| Mouth: | Pacific Ocean |
| Mouth Location: | New Zealand |
| Mouth Coordinates: | -42.7778°N 173.3719°W |
| Mouth Elevation: | 0m (00feet) |
| Basin Size: | 3310km2 |
| Tributaries Left: | Stanley River, Edwards River, Grantham River, Percival River, Hanmer River, Mason River, Stanton River, Leader River |
| Tributaries Right: | Ada River, Henry River, Hope River |
Waiau Uwha River, previously known as the Waiau River, is a river in north Canterbury in the South Island of New Zealand. The Waiau Uwha River rises in the Spenser Mountains and flows eastward to the Pacific Ocean. The Waiau Uwha River has the second largest catchment—3310km2—of North Canterbury's rivers.[1] In 2018, the name of the river was officially changed from Waiau River to Waiau Uwha River, to reflect its original Māori name,[2] and to distinguish it from the longer Waiau River in the southern South Island.