Rio Santa Maria do Rio Doce is a river located in Espírito Santo, Brazil, flowing through a region of significant ecological importance within the broader Rio Doce basin. The river drains the eastern slopes of the Santa Teresa Mountains and is recognized as part of a distinct area of endemism, harboring several fish species found nowhere else on earth. A dam — the Barragem de Santa Maria do Doce, operated by Empresa Luz e Força Santa Maria (ELFSM) — is a notable infrastructure feature on the river, creating a reservoir environment that adds variety to the fishing opportunities available along this waterway. The river's position at the interface between the upper and lower Rio Doce drainage systems gives it a unique ichthyological character, blending species assemblages from both the western interior and the Atlantic coastal lowlands of Espírito Santo.