It is the only living member of the genus Theropithecus, a name derived from the Greek root words for "beast-ape" (θηρο-πίθηκος : thēro-píthēkos).

[3][4] Like its close relatives in genus Papio, the baboons, it is largely terrestrial, spending much of its time foraging in grasslands, with grasses comprising up to 90% of its diet.

Adult males have longer hair on their backs and a conspicuous bright red patch of skin shaped like an hourglass on their chests.

Females also have a bare patch of skin but it is less pronounced, except during estrus, when it brightens and exhibits a "necklace" of fluid-filled blisters.

[8] Theropithecus, while restricted at present to Ethiopia, is also known from fossil specimens found in Africa and the Mediterranean into Asia, including South Africa, Malawi, the Democratic Republic of the Congo, Tanzania, Uganda, Kenya, Algeria, Morocco, Spain, and India (more exactly at Mirzapur, Cueva Victoria, Pirro Nord, Ternifine, Hadar, Turkana, Makapansgat, and Swartkrans).

Since the 1990s, however, molecular phylogenetic studies [9] clarified relationships among papionin monkeys, demonstrating that mangabeys of the genus Lophocebus are more closely related to Papio and Theropithecus, while mangabeys of the genus Cercocebus are more closely related to Mandrillus.

These findings largely invalidated any scientifically based justification for referring to mandrills and drills as baboons, as doing so while excluding the unbaboon-like Lophocebus mangabeys would create a polyphyletic group.

The status of geladas was less clear and the relationships among Papio, Lophocebus, and Theropithecus continue to reflect high levels of uncertainty, which are further complicated by the discovery of the kipunji.

Nevertheless, the most recent and extensive phylogenetic study to date demonstrates that, while large fractions of the genome show an alternative history, the dominant relationship across the genome supports a closer relationship between Papio and Lophocebus, with Theropithecus as the outgroup.

[10] As a close sister relationship between Papio and Theropithecus is the least-supported scenario in recent studies, i "gelada baboon" and other names implying a close relationship with baboons, with increasing clarity, are not scientifically justified, leading researchers to advocate for the common name to be simply "gelada".

[11] The gelada is large and robust, and it is covered with buff to dark-brown, coarse hair and has a dark face with pale eyelids.

[15] Because of this gait, the gelada's rump is hidden beneath, so is unavailable for display; its bright red chest patch is visible, though.

They live in elevations 1,800–4,400 m (5,900–14,400 ft) above sea level, using the cliffs for sleeping and montane grasslands for foraging.

[15] When morning ends, social activities tend to wane and the geladas primarily focus on foraging.

[15] Predators observed to hunt geladas include domestic dogs, leopards, servals, hyenas, and lammergeiers.

[22] While geladas have traditionally been considered to have a male-transfer society, many males appear to be likely to return and breed in their natal bands.

The male maintains his relationship with the females by grooming them rather than forcing his dominance, in contrast to the society of the hamadryas baboon.

Researchers from the University of the Free State in South Africa, while observing gelada during field studies, discovered that the monkeys were capable of "cheating" on their partners and covering up their infidelity.

Dr. Aliza le Roux of the university's Department of Zoology and Entomology believes that dishonesty and punishment are not uniquely human traits, and that the observed evidence of this behaviour among gelada monkeys suggests that the roots of the human system of deceit, crime, and punishment lie very deep indeed.

In stark contrast, the geladas always fled great distances to the cliffs for safety whenever they encountered aggressive domestic dogs.

[35] If a new male assumes mastery of a harem, females impregnated by the previous leader have an 80% likelihood of aborting, in a phenomenon known as the Bruce effect.

[36] Females come into estrus quickly after giving birth, so males have little incentive for practising infanticide, although it does occur in some communities in the Arsi region of Ethiopia, which may be an incentive for females to abort and avoid investing caring for an infant that will most likely be killed.

[37] Infanticide in geladas remains fairly uncommon, though, compared to many primates that live in one-male units such as gorillas or gray langurs.

[38] When a male loses his position as dominant harem master, the females and new leader may allow him to remain in the social unit as a nonbreeding resident to act as a babysitter.

This way, the ex-leader can protect any infants he had fathered from being killed by the new leader, the females can protect the infants fathered by him, and when the new leader faces a potential rival, the ex-leader will be more inclined to help support him in keeping rivals at bay.

Mortality among infants occurs at its highest in the wet season, but on average, over 85% of infants survive to their fourth birthday, one of the great advantages of living in an environment with a food source few other animals can exploit, so is unable to sustain many large predators.

[41] Adult geladas use a diverse repertoire of vocalizations for various purposes, such as: contact, reassurance, appeasement, solicitation, ambivalence, aggression, and defense.

In 2016, a research group at the University of Michigan found that gelada vocalizations obey Menzerath's law, observing that calls are abbreviated when used in longer sequences.

[2] Major threats to the gelada are a reduction of their range as a result of agricultural expansion and shooting as crop pests.

Previously, these monkeys were trapped for use as laboratory animals or hunted to obtain their capes to make items of clothing.