The Abuna River is a river in South America. As a part of the Amazon Basin, it forms part of the border between northern Bolivia and north-western Brazil. The river has a total length of 375 km. It originates in several streams east of the Cordillera Oriental of the Peruvian Andes. The river is navigable for circa 320 km in its lower northeastern part. At Manoa it joins the Río Madeira, a tributary of the Amazon. Opposite the river mouth is the town of Abunã on the Brazilian side of the confluence.