The extinct big cat commonly called the saber-toothed tiger is Smilodon.
Smilodon was a genus of machairodont felids that lived in the Americas from the Pleistocene into the early Holocene. Its best-known species include Smilodon fatalis, common in North America, Smilodon gracilis and the larger South American Smilodon populator. The genus is famous for its extremely long upper canine teeth and powerful forelimbs.
The nickname “saber-toothed tiger” is useful but scientifically misleading. Smilodon was not a tiger and was not closely related to modern cats such as Panthera tigris. It belonged to the extinct subfamily Machairodontinae, which diverged from the lineage leading to living cats roughly 20 million years ago. Other saber-toothed predators, including Megantereon and Homotherium, were separate genera.
Fossils from California’s La Brea Tar Pits form the largest known collection of Smilodon remains. Scientists think it restrained large prey with its forelimbs before delivering a precise bite, but debates continue over its hunting style, social behavior and exact appearance.