Grande River, Portuguese Rio Grande, river, south-central Brazil. It rises in the Mantiqueira Mountains almost in sight of Rio de Janeiro city and descends inland, west-northwestward, in many falls and rapids. Its lower course marks a portion of the Minas Gerais–São Paulo border. At the Mato Grosso do Sul state border, after a course of 845 miles (1,360 km), it joins the Paranaíba River to form the Alto (Upper) Paraná River. The Márimbondo Waterfalls, 35 miles (56 km) north of São José do Rio Prêto, have hydroelectric potential. The Grande is navigable for about 130 miles (210 km) above the falls.