The Tumbes River, is a river in South America. The river's sources are located between Ecuadorian El Oro and Loja provinces. It is the border between El Oro and Loja, and afterwards the border between Loja and the Tumbes Region in Peru. At its confluence with the Cazaderos stream, it enters the northern coastal region of Peru called the Tumbes Region, and flows into the Pacific Ocean outside the Gulf of Guayaquil. The largest city on its banks is Tumbes, Peru.