The Cuyuni River is a South American river and a tributary of the Essequibo River. It rises in the Guiana Highlands of Venezuela where it descends northward to El Dorado, and turns eastward to meander through the tropical rain forests of Guyana. It finally turns southeastward, flowing to its confluence with the Mazaruni River. The Cuyuni River marks the limit of the disputed territory of Guayana Esequiba for approximately 100 kilometres (62 mi). Some of the Kali'na people live in the Cuyuni River valley, part of which is in Guyana. The river is a source of alluvial gold.