Ischigualastia is an extinct genus of large dicynodont therapsids from the Late Triassic (Carnian) Ischigualasto Formation of Argentina (from which the genus takes its name). The type species and only known species, I. jenseni, was named in 1962 by C. Barry Cox, who wrote a more detailed description three years later. The species name honours James Jensen, who prepared some of the earliest fossils. There are some reports of Ischigualastia remains outside of Argentina, though these do not hold up to scrutiny.

Ischigualastia was a large dicynodont, with an estimated body mass of 1,000 kg (2,200 lb). Its skull would have measured up to 60 cm (2.0 ft) in length; the holotype skull, the specimen on which the genus is founded, measured 55 cm (1.80 ft) in length and 46 cm (1.51 ft) in width. Like some other stahleckeriids, Ischigualastia had a pair of large protrusions towards the front of its upper jaw. Known as caniniform processes, these structures superficially resemble tusks (and in some genera, such as Placerias, did support them). Ischigualastia had deep zygomatic arches (cheek bones) which were angled upwards. The shoulder bones of Ischigualastia are very robust.

Like other Late Triassic dicynodonts, Ischigualastia is a member of the family Stahleckeriidae, though it was originally assigned to Kannemeyeriidae. It was among the largest herbivores of the Ischigualasto Formation, alongside its later relative, Jachaleria.

Ischigualastia was briefly named by C. Barry Cox in 1962, with a larger description published in 1965. It is one of the better-known South American dicynodonts in terms of its variety of fossils, including several nearly complete skulls. Cox named the genus after its location of discovery, the Ischigualasto Valley, while the species honors James Jensen, who prepared some of its fossils.

The holotype, MACN 18.055, is a skull stored at the Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN) in Buenos Aires. Though partially "restored" with plaster, it still closely resembles unaltered skulls. Cox in 1965 also discussed Ischigualastia fossils collected by the Museum of Comparative Zoology (MCZ) in Cambridge, Massachusetts. Additional fossils are housed at the Instituto Miguel Lillo (PVL) in Tucumán and Universidad Nacional de San Juan (PVSJ) in San Juan. However, they have yet to be fully described.

There are a few reports of Ischigualastia fossils from New Mexico, Texas, and India: a femur, a snout fragment, and a poorly-preserved skull, respectively. These claims have not held up to scrutiny, since the fossils in question do not closely resemble Ischigualastia in particular. Supposed Ischigualastia fossils from Brazil are more likely to be Jachaleria, Sangusaurus, or a new unnamed species.

Ischigualastia is a member of the family Stahleckeriidae, a clade which includes some of the biggest dicynodonts. It is similar in stature to the North American stahleckeriid Placerias, which measured around 3.5 metres (11 ft) long and weighed up to 800–1,000 kilograms (1,800–2,200 lb). Indeed, Lucas Fiorelli and colleagues estimated in 2013 that the holotype specimen of Ischigualastia would have weighed around 1,000 kg (2,200 lb).

Ischigualastia is a very large dicynodont. The skull had a maximum known length of 60 cm (2.0 ft), though the holotype skull measured 55 cm (1.80 ft) long and 46 cm (1.51 ft) across. The skull was deep and bore pointed projections (known as caniniform processes) on each side of the snout, rather than true tusks; this condition is seen in several other stahleckeriids. The back of the skull is steeply sloped and has particularly large spaces for vertical jaw muscles, suitable for a strong bite. In contrast, many earlier tusked dicynodonts had low skulls which were better suited for propalinal (front-to-back) jaw movement during a bite.