| Jamari River | |
| Map Size: | 300 |
| Pushpin Map Size: | 300 |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
| Subdivision Type2: | State |
| Subdivision Name2: | Rondônia |
| Subdivision Type5: | City |
| Subdivision Name5: | Itapuã do Oeste |
| Length: | 400km (200miles)[1] |
| Source1: | Pacaás Novos mountain range |
| Source1 Location: | Campo Novo de Rondonia, Rondônia, Brazil |
| Source1 Coordinates: | -11.1°N -63.3167°W |
| Source1 Elevation: | 460m (1,510feet) |
| Mouth: | Madeira River |
| Mouth Location: | Porto Velho, Rondônia, Brazil |
| Tributaries Left: | Candeias River Verde River (Jamari River) |
| Tributaries Right: | Preto do Crespo River Guaiamã River Branco River (Jamari River) |
The Jamari River is a river of Rondônia state in western Brazil.
Part of the river's watershed is covered by the Jacundá National Forest, a sustainable use conservation unit.The Jamari river is dammed by the Samuel Hydroelectric Dam near Porto Velho, which forms a reservoir that covers . The Samuel Ecological Station was established in compensation for the environmental impact. The ecological station extends to the east of the dam and protects part of the Jamari river basin.