Wildebeest ( WIL-dib-eest, VIL-, ), also called gnu ( NEW or NOO), are antelopes of the genus Connochaetes and native to Eastern and Southern Africa. They belong to the family Bovidae, which includes true antelopes, cattle, goats, sheep, and other even-toed horned ungulates. There are two species of wildebeest: the black wildebeest or white-tailed gnu (C. gnou), and the blue wildebeest or brindled gnu (C. taurinus).

Fossil records suggest these two species diverged about one million years ago, resulting in a northern and a southern species. The blue wildebeest remained in its original range and changed very little from the ancestral species, while the black wildebeest changed more as adaptation to its open grassland habitat in the south. The most obvious ways of telling the two species apart are the differences in their colouring and in the way their horns are oriented.

In East Africa, the blue wildebeest is the most abundant big-game species; some populations perform an annual migration to new grazing grounds, but the black wildebeest is merely nomadic. Breeding in both takes place over a short period of time at the end of the rainy season and the calves are soon active and are able to move with the herd, a fact necessary for their survival. Nevertheless, some fall prey to large carnivores, especially the spotted hyena.

Wildebeest often graze in mixed herds with zebra, which gives heightened awareness of potential predators. They are also alert to the warning signals emitted by other animals such as baboons. Wildebeest are a tourist attraction but compete with domesticated livestock for pasture and are sometimes blamed by farmers for transferring diseases and parasites to their cattle. Illegal hunting does take place but the population trend is fairly stable. Wildebeest can also be found in national parks or on private land. The International Union for Conservation of Nature lists both kinds of wildebeest as least-concern species.