Porto Alegre, city, capital of Rio Grande do Sul estado (state), southern Brazil. It lies near the Atlantic Ocean coast at the northern end of the freshwater Patos Lagoon along an arm of the lagoon known as the Guaíba River. The city is situated at the junction of five short but deep rivers that flow into the Patos Lagoon.
Founded in 1742–43 by colonists from the Azores, the city was first known as Porto dos Casais (or Porto dos Cazaes). In 1825 the first German immigrants settled near the site, to be joined later by Italian settlers. The administrative centre of Rio Grande do Sul was moved in 1773 from Rio Grande to Porto Alegre, which officially became the state’s capital in 1807.