| Machadinho River | |
| Pushpin Map: | Brazil |
| River System: | Jiparaná River |
| Mouth Location: | Jiparaná River, Campos Amazônicos National Park |
| Mouth Coordinates: | -9.0275°N -61.7951°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
The Machadinho River (pt|Rio Machadinho) is a river of Rondônia state in western Brazil, a tributary of the Jiparaná River.
The river runs along the western boundary of the Seringueira Extractive Reserve, one of a number of small sustainable use units in the region whose primary product is rubber.