Paraná River (Spanish, a river in southeastern South America. It is formed by the union of the Grande and Paranaíba rivers in southern Brazil. The Parana flows generally southward for about 1,900 miles (3,060 km) and empties into the Río de la Plata, which flows into the Atlantic Ocean. The Paraná joins the Río de la Plata in the vicinity of Buenos Aires, Argentina.

The river forms part of the Brazil-Paraguay and Paraguay-Argentina borders. On the Paraguay-Argentina border the Paraná is met by its main tributary, the Paraguay River. The Paraná and its tributaries drain parts of Bolivia, Paraguay, Brazil, and Argentina, forming one of the largest river basins in South America. The lower Paraná is navigable up to its junction with the Paraguay River.

The basin of the Paraná is sparsely inhabited and little developed, but has the resources to become one of the richest regions on the continent. The hydroelectric potential is enormous. A number of large dams have been built, including the Itaipu Dam, a Brazilian-Paraguayan project, which has the greatest generating capacity of any hydroelectric project in the world.

The first European to ascend the Paraná was Sebastian Cabot in 1526.