Nhamundá River or Jamundá River (Yamundá River in Spanish) is a river in northern Brazil, which marks part of the northeastern boundary between states of Amazonas and Pará. The 300 km long Nhamundá River originates in the plateau near the division of the Brazilian States of Roraima, Amazonas and Pará, and from there it flows in a southeastern direction, forming the natural division between Amazonas and Pará. It then crosses the (EG033) before joining the Trombetas River near the city of Oriximiná. The river, which flows through the , is the last major right-hand affluent of the Trombetas River before the Trombetas joins the Amazon River. The mouth is located about 480 km east (downstream on the Amazon) of Manaus.