The Amazon is the world's largest tropical rainforest.
It's one of Brazil's most spectacular natural features and there are three million different species of plants and animals there.
But for years people have been cutting down the trees and there are concerns the rainforest is going to be destroyed.
On Saturday, England will play their first World Cup match in the city of Manaus which is in the rainforest.
Leah visited the rainforest to find out more.