The Parnaíba River is a river in Brazil, which forms the border between the states of Maranhão and Piauí. The Parnaíba River rises in the Chapada das Mangabeiras range, and flows northeastward for 1,056 miles (1,700 kilometers) to empty into the Atlantic Ocean, being the longest river entirely located within Brazil's Northeast Region[1] . The middle and upper regions of this river are separated by waterfalls, but is otherwise navigable.