The Paraná River (Spanish: Río Paraná, Portuguese: Rio Paraná) is a river in south Central South America, running through Brazil, Paraguay and Argentina for some 4,880 kilometres (3,030 mi). It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language and means "like the sea" (that is, "as big as the sea"). It merges first with the Paraguay River and then farther downstream with the Uruguay River to form the Río de la Plata and empties into the Atlantic Ocean.

The course is formed at the confluence of the Paranaiba and Grande rivers in southern Brazil. From the confluence the river flows in a generally southwestern direction for about 619 km (385 mi) before encountering the city of Saltos del Guaira, Paraguay. This was once the location of the Sete Quedas waterfall, where the Paraná fell over a series of seven cascades. This natural feature was said to rival the world famous Iguazu Falls to the south. The falls were flooded, however, by the construction of the Itaipu dam, which began operating in 1984.