Rio Branco is a Brazilian municipality, capital of the state of Acre. Located in the valley of the Acre River in northern Brazil, it is the most populous municipality in the state, with 387,852 inhabitants, according to 2024 IBGE estimates, almost half the state population. Rio Branco was one of the first settlements to develop in the region, being the westernmost major settlement in the country and the 4th-oldest state capital city in Northern Brazil, after Belém, Manaus and Macapá.