Brazil has the largest mammal diversity in the world, with more than 600 described species and more likely to be discovered. According to the International Union for Conservation of Nature, 66 of these species are endangered, and 40% of the threatened taxa belong to the primate group. 658 species are listed. The following tags are used to highlight each species' conservation status as assessed by the International Union for Conservation of Nature: Some species were assessed using an earlier set of criteria. Species assessed using this system have the following instead of least concern categories:

Infraclass: Metatheria

Order: Didelphimorphia

Infraclass: Eutheria

Order: Pilosa

Order: Cingulata

Order: Chiroptera

Order: Primates

Order: Carnivora

Canidae - dogs, foxes, wolves

Felidae - cats

Mustelidae - otters, weasels and allies

Mephitidae - skunks

Otariidae - eared seals

Phocidae - earless seals

Procyonidae - raccoons, coatis, olingos and allies

Cetacea

Balaenidae - right whales

Balaenopteridae - rorquals

Delphinidae - dolphins

Phocoenidae - porpoises

Physeteridae

Iniidae - South American river dolphins

Pontoporiidae - La Plata dolphin

Ziphiidae - beaked whales

Sirenia

Trichechidae - manatees

Perissodactyla

Tapiridae - tapirs

Artiodactyla

Suidae - pigs

Tayassuidae - peccaries

Cervidae - deer

Rodentia

Sciuridae - squirrels

Myocastoridae

Muridae - Old World rats and allies

Cricetidae - New World rats and allies

Erethizontidae - New World porcupines

Dinomyidae

Caviidae - guinea pigs and cavies

Hydrochaeridae

Dasyproctidae - agoutis and acouchis

Cuniculidae

Ctenomyidae - tuco-tucos

Echimyidae - spiny rats and allies

Lagomorpha

Leporidae - rabbits and hares