| Piranhas River | |
| Source1 Location: | Tocantins state |
| Mouth: | Araguaia River |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
The Piranhas River is a river of Tocantins state in central Brazil. The Piranhas discharges into the Araguaia River in northern Tocantins state near the municipality of Araguatins. Both the Araguaia and the Piranhas form part of the Tocantins basin.