The Rio Abunã is a significant Amazonian river stretching approximately 500 kilometers through the remote borderlands of northwestern Brazil and northern Bolivia, forming a natural boundary between the two countries within the Pando Department region. Fed by streams originating east of the Cordillera Oriental of the Peruvian Andes, this river is a true tributary of the greater Amazon Basin, ultimately joining the Rio Madeira near the confluence town of Abunã on the Brazilian side. The lower northeastern portion of the river — roughly 320 kilometers — is navigable, making it accessible by boat through much of its length. This is a wild, frontier waterway set deep within the Amazon rainforest, offering an extraordinary and remote fishing experience far from the pressures of heavily visited destinations.