The Zarumilla River is a river in South America that marks the border between Peru and Ecuador. It is named after the Peruvian town of Zarumilla. It is part of the Gulf of Guayaquil-Tumbes mangroves Sanctuary and its currents, sediments, and tides strongly influence the geomorphology of the area. It empties into the Gulf of Guayaquil. The largest towns on its banks are Huaquillas, in the Ecuadorian province of El Oro, and Aguas Verdes in the Tumbes Region of Peru; both towns are connected by an international bridge.