Rio Itacaiúnas is a significant river system flowing through the state of Pará in Brazilian Amazonia, draining the Serra dos Carajás region — one of the most ecologically rich and geologically distinctive areas in the Amazon basin. The river winds through dense tropical forest and is closely associated with the broader Tocantins basin system. The Itacaiúnas drainage encompasses a variety of aquatic habitats shaped by the region's geology, including the iron-rich highlands of the Carajás mountain range, giving the watershed a character unlike many other Amazonian rivers. The river supports a diverse assemblage of fish species, reflecting the high biodiversity typical of Amazonian drainages, while also facing pressures from large-scale mining operations in the surrounding region.