Bison are large bovines in the genus Bison (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised.

Of the two surviving species, the American bison, B. bison, found only in North America, is the more numerous. Although colloquially referred to as a buffalo in the United States and Canada, it is only distantly related to the true buffalo. The North American species is composed of two subspecies, the Plains bison, B. b. bison, and the wood bison, B. b. athabascae, which is the namesake of Wood Buffalo National Park in Canada. A third subspecies, the eastern bison (B. b. pennsylvanicus) is no longer considered a valid taxon, being a junior synonym of B. b. bison. References to "woods bison" or "wood bison" from the eastern United States refer to this subspecies, not B. b. athabascae, which was not found in the region. The European bison, B. bonasus, or wisent, or zubr, or colloquially European buffalo, is found in Europe and the Caucasus, reintroduced after being extinct in the wild.

While bison species have been traditionally classified in their own genus, modern genetics indicates that they are nested within the genus Bos, which includes, among others, cattle, yaks and gaur, being most closely related to yaks. Bison are sometimes bred with domestic cattle and produce offspring called beefalo or zubron.