Guaíba is a major water body in Rio Grande do Sul, the southernmost state of Brazil. It is commonly referred to either as a "river" or as a "lake". The Jacuí River, the Sinos River, the Gravataí River and the Caí River empty into Guaíba from the north, which in its turn empties into the Lagoa dos Patos, the largest lagoon in South America further down south. The body of water covers 496 square kilometres (192 sq mi) in total.