The longest river in South America is the Amazon River. It is about 4,000 miles long and can be as wide as 120 miles in the rainy season.
No one is quite sure where the source of the Amazon River is. In fact, scientists have suggested as many as five places that might be the source of the river, though it does begin somewhere in the Andes Mountains. It flows through seven countries, mostly through rainforests, before emptying into the Atlantic Ocean. The river harbors a large number of animals, including thousands of species of fish, such as piranha, as well as anacondas, giant snakes that attack other animals and fish.