Porto Alegre is the capital and largest city of the Brazilian state of Rio Grande do Sul. Its population of 1.3 million inhabitants makes it the 1…Porto Alegre is the capital and largest city of the Brazilian state of Rio Grande do Sul. Its population of 1.3 million inhabitants makes it the 11th-most populous city in the country and the center of Brazil's fifth-largest metropolitan area, with 4.4 million inhabitants. The city is the southernmost capital city of a Brazilian state.