The longest river in South America is the Amazon River. It spans approximately 4,345 miles (7,062 kilometers) from its source in the Andes Mountains of Peru to its mouth at the Atlantic Ocean in Brazil. The Amazon River is not only the longest river in South America but is also considered one of the longest rivers in the world. It flows through diverse ecosystems, including the world’s largest tropical rainforest, the Amazon rainforest, which hosts an incredible variety of plant and animal species. The river plays a crucial role in the region's ecology and economy, providing resources and transportation.