Which river is the longest in South America?

 The longest river in South America is the Amazon River.

Key Facts about the Amazon River:

• Length: Approximately 7,000 kilometers (4,350 miles), though exact measurements vary depending on the source.
• Location: Flows through several countries, primarily Peru and Brazil.
• Discharge: It has the largest volume of water discharge of any river in the world.
• Basin: The Amazon Basin is the largest rainforest and river basin on Earth, home to incredible biodiversity.