The Amazon basin is the largest drainage basin in the world, more than twice as large as that of the Congo River in Africa. Approximately one-fifth of all freshwater runoff on Earth passes through this watershed.

The Amazon Basin possesses two unparalleled geographical and biological features: its massive freshwater output and its unmatched biodiversity. First, the Amazon River is the largest in the world by discharge volume, providing roughly 20% of all the freshwater that enters the Earth's oceans. Its flow is so powerful that it dilutes the salinity of the Atlantic Ocean for over 100 miles beyond the river's mouth. Second, the basin contains the world's largest tropical rainforest, which acts as a "biological heart" for the planet. It is home to an estimated 10% of all known species on Earth, including over 40,000 plant species and 2.5 million insect species. A unique 2026 perspective on this basin also highlights its "Flying Rivers"—the process where the forest's billions of trees release 20 billion tonnes of moisture into the atmosphere daily, creating a self-sustaining weather system that regulates rainfall across the entire South American continent, far beyond the borders of the rainforest itself.