The São Gonçalo Channel is a navigable channel connecting two large coastal lagoons, Lagoa Mirim and Lagoa dos Patos, in the state of Rio Grande do Sul in southern Brazil. At its eastern end, it separates the municipalities of Rio Grande to the south from Pelotas to the north.

Lagoon Mirim or Merín is a large estuarine lagoon which extends from southern Rio Grande do Sul state in Brazil into eastern Uruguay. Lagoa Mirim is separated from the Atlantic Ocean by a sandy, partially barren isthmus.