The Abuna River is a river in South America. As a part of the Amazon Basin

Amazon Basin

The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

, it forms part of the border between northern Bolivia

Bolivia

Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

 and north-western Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

.

The river has a total length of 375 kilometres (233 mi). It originates in several streams east of the Cordillera Oriental

Cordillera Oriental, Peru

The section of the Cordillera Oriental in Peru is in the extreme south-west of the area of study, where manifestation like the spurs of the eastern flank. This unit has modelled itself on metamorphic rocks of the Paleozoic. The eastern limit is more or less uniform and Colorado is located in the...

 of the Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

vian Andes

Andes

The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

. The river is navigable for circa 320 kilometres (198.8 mi) in its lower northeastern part. At Manoa it joins the Río Madeira, a tributary of the Amazon. Opposite the river mouth there is the town of Abunã

Abunã

Abunã is a town in the Rondônia state of Brazil. It is situated in the Amazon Basin on the right bank of the Madeira River 10 km upstream from its confluence with the Abuna River. The Abuna River and the Madeira River upstream from their confluence mark the boundary between Brazil and Bolivia,...

on the Brazilian side of the confluence.