Orinoco River, one of the great rivers of South America. It flows through the northern part of the continent, draining parts of Venezuela and Colombia. The Orinoco begins in southern Venezuela near the Brazilian border and flows some 1,600 miles (2,600 km) in a curving, northeasterly course to the Atlantic Ocean. At the river's mouth is a large delta with a main channel and numerous branches. In annual flow the Orinoco is exceeded only by the Amazon and the Congo.

The Orinoco's drainage basin occupies roughly 340,000 square miles (880,000 km2) and is covered mostly by tropical rain forests and savannas. Major tributaries include the Apure, Carom, Guaviare, and Meta rivers. The Casiquiare River links the Orinoco and Amazon systems.

Most of the Orinoco's basin is sparsely settled; much of the upper part is largely unexplored. Economic development is mainly in the Ciudad Bolivar and Ciudad Guayana areas of Venezuela, where abundant hydroelectric power and the iron, steel, and aluminum industries are bringing rapid growth. Both cities are accessible to oceangoing ships.