Lagoa dos Patos is the largest lagoon in Brazil and the largest coastal lagoon in South America. It is located in the state of Rio Grande do Sul, southern Brazil. It covers an area of 10,100 km2 (3,900 sq mi), is 180 miles (290 km) long and has a maximum width of 44 miles (71 km).
Lagoa dos Patos is separated from the Atlantic Ocean by a sandbar about 5 miles (8.0 km) wide. The lagoon receives the Jacuí River (via the Guaíba River) in the north and the Mirim Lagoon overflow (via the São Gonçalo Canal) in the south. A mile-wide channel leads to the Atlantic at the city of Rio Grande in the south. The dredged channel allows vessels to ply between Rio Grande and Porto Alegre, the state capital. The waters of the Patos Lagoon are fished.