| Mārahau River | |
| Pushpin Map: | New Zealand#New Zealand South Island |
| Pushpin Map Size: | 270px |
| Pushpin Map Caption: | Mouth of the Mārahau River |
| Source1 Location: | Mount Evans |
| Source1 Coordinates: | -40.9512°N 172.9263°W |
| Mouth Location: | Sandfly Bay |
| Mouth Coordinates: | -40.9978°N 173.007°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Progression: | Mārahau River → Sandy Bay → Tasman Bay → Tasman Sea |
The Mārahau River is a river of the Tasman Region, New Zealand. The river originated on the eastern slopes of Mount Evans in the Abel Tasman National Park, and flows south-east towards Sandy Bay, a bay of Tasman Bay, north of the village of Mārahau.