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.