River, northeastern Brazil.
It rises in the Tabatinga Mountains and flows northeast for 600 mi (965 km) to empty into the Atlantic Ocean, forming a delta at its mouth. The river has great economic importance. It is navigable by shallow-draft vessels from its mouth at least as far south as the junction of the Canindé River. The port of Parnaíba (pop., 2002 est.: 128,100), located near the river's mouth, is a commercial centre.