Bison (also called buffalo) are large, even-toed ungulates in the genus Bison within the subfamily Bovinae.

Two extant and four extinct species are recognized. Of the four extinct species, three were North American: Bison antiquus, B. latifrons, and B. occidentalis. The fourth, B. priscus, ranged across steppe environments from Western Europe, through Central Asia, and onto North America.

Of the two surviving species, the American bison, B. bison, found only in North America, is the more numerous. (Although sometimes referred to as a "buffalo", 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. The European bison B. bonasus, or wisent, is found in Europe and the Caucasus, reintroduced after being extinct in the wild.

While all bison species are usually grouped into their own genus, they are sometimes included in the closely related genus Bos,[1] together with cattle, gaur, kouprey, and yaks, with which bison have a limited ability to interbreed.