There are a total of 644 Mammals compiled and organized in this comprehensive list. The selection includes extant, commonly accepted species drawn from authoritative sources (IUCN Red List, Mammal Species of the World, GBIF, EOL), with habitats standardized and average adult length recorded in centimetres.

Mammals are warm-blooded vertebrates that bear hair or fur, produce milk for their young, and usually give live birth. They range from tiny shrews and bats to the blue whale and occupy nearly every habitat on Earth. Mammals play key ecological roles as predators, prey, pollinators and ecosystem engineers. Their diversity supports research in evolution, conservation and medicine, and underpins many cultural and economic activities.

Interesting and little-known facts about Mammals:
– There are about 6,400 extant mammal species worldwide; rodents account for roughly 2,277 species and bats about 1,400 species.
– About 25% of assessed mammal species are listed as threatened on the IUCN Red List.
– The blue whale is the largest mammal, reaching about 30 metres and over 150,000 kg; the Etruscan shrew weighs around 1.8 g and the bumblebee bat is roughly 3 cm long.
– Monotremes comprise only five living species (the platypus and four echidnas) and are the only egg-laying mammals.
– Several mammal groups, including many bats and toothed whales, use echolocation—biological sonar—for navigation and hunting.

The A–Z index links to individual letter pages that list species by their initial letter. Each entry includes the common name, scientific name, habitat (forest, grassland, freshwater, marine, desert, urban), and average adult length in centimetres (cm).