The Atlantic Forest (Portuguese: Mata Atlântica) is a region of tropical and subtropical moist forest, tropical dry forest, tropical savanna, semi-deciduous forest and mangrove forests which extends along the Atlantic coast of Brazil from Rio Grande do Norte state in the north to Rio Grande do Sul state in the south, and inland as far as Paraguay and the Misiones Province of Argentina. The Atlantic Forest is characterized by a high species diversity and endemism. It was the first environment that the Portuguese conquerors encountered over 500 years ago when it was thought to have had an area of 1,000,000 to 1,500,000 km² (390,000 to 580,000 sq mi) and stretching an unknown distance inland. Currently, the Atlantic Forest spans over 4,000 km² (1,500 sq mi) along the coast of Brazil and in a small part of Paraguay and Argentina. In Argentina, it is known as Selva Atlántica.

The Atlantic Forest region includes forests of several variations:

The Atlantic Forest is unusual in that it extends as a true tropical rainforest to latitudes as high as 24°S. This is because the trade winds produce precipitation throughout the southern winter. In fact, the northern Zona da Mata of northeastern Brazil receives much more rainfall between May and August than during the southern summer.