Paraná River, Portuguese Rio Paraná, Spanish Río Paraná, river of South America, the second longest after the Amazon, rising on the plateau of southeast-central Brazil and flowing generally south to the point where, after a course of 3,032 miles (4,880 km), it joins the Uruguay River to … The Parana River begins in Brazil, at the Paranaiba River, and ends in the Atlantic Ocean, near Buenos Aires in Argentina. The Parana River begins in Brazil, at the Paranaiba River, and ends in the Atlantic Ocean, near Buenos Aires in Argentina. Parana river ends in Argentina, Paraguay.