Lençóis Maranhenses National Park (Parque Nacional dos Lençóis Maranhenses) is a national park located in Maranhão state in northeastern Brazil, just east of the Baía de São José. Protected on June 2, 1981, the 155,000 ha (380,000-acre) park includes 70 km (43 mi) of coastline, and an interior composed of rolling sand dunes.

During the rainy season, the valleys among the dunes fill with freshwater lagoons, prevented from draining due to the impermeable rock beneath. The park is home to a range of species, including four listed as endangered, and has become a popular destination for ecotourists.

The lagoons in the park are often interconnected with one another, as well as with the rivers that run through the area. They are home to a number of fish and insect species, including the wolf fish, which burrows down into wet layers of mud and remains dormant during the dry season. Besides the dunes that form the centerpiece of the park, the ecosystem also includes area of restinga and mangrove ecosystems. 

The park is home to four species listed as endangered, the scarlet ibis (Eudocimus ruber), the neotropical otter (Lontra longicaudis), the oncilla (Leopardus tigrinus) and the West Indian manatee (Trichechus manatus). The park also includes 133 species of plants, 112 species of birds, and at least 42 species of reptiles. 

According to en.wikipedia