| Opitonui River | |
| Source1 Location: | Coromandel Range |
| Mouth Location: | Whangapoua Harbour |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Length: | 100NaN0 |
The Opitonui River is a river of the Coromandel Peninsula in New Zealand's North Island. It flows north to reach the peninsula's east coast at Whangapoua Harbour, close to the small settlement of Te Rerenga. The river provides a water supply for Matarangi by way of a pipe laid across the Whangapoua harbour.