The Pantanal is a natural region encompassing the world's largest tropical wetland area, and the world's largest flooded grasslands. It is located mostly within the Brazilian state of Mato Grosso do Sul, but it extends into Mato Grosso and portions of Bolivia and Paraguay. It sprawls over an area estimated at between 140,000 and 195,000 square kilometres (54,000 and 75,000 sq mi). Various subregional ecosystems exist, each with distinct hydrological, geological and ecological characteristics; up to 12 of them have been defined.
Roughly 80% of the Pantanal floodplains are submerged during the rainy seasons, nurturing a biologically diverse collection of aquatic plants and helping to support a dense array of animal species.
The name "Pantanal" comes from the Portuguese word pântano, meaning wetland, bog, swamp, quagmire or marsh. By comparison, the Brazilian highlands are locally referred to as the planalto, plateau or, literally, high plain.