Chinchilla is a genus consisting of two species (Chinchilla chinchilla and Chinchilla lanigera) of crepuscular rodents of the parvorder Caviomorpha, native to the Andes Mountains in South America. They live in colonies called "herds" at high elevations up to 4,270 m (14,000 ft). Historically, chinchillas lived in an area that included parts of Bolivia, Peru and Chile, but today, colonies in the wild are known only in Chile. Along with their relatives, viscachas, they make up the family Chinchillidae. They are also related to the chinchilla rat.

The chinchilla has the densest fur of all extant terrestrial mammals, with around 20,000 hairs per square centimeter and 50 hairs growing from each follicle. The chinchilla is named after the Chincha people of the Andes, who once wore its dense, velvet-like fur and ate their meat. By the end of the 19th century, chinchillas had become quite rare after being hunted for their notably soft fur. Most chinchillas currently used by the fur industry for clothing and other accessories are farm-raised. Domestic chinchillas descended from C. lanigera are sometimes kept as pets, and may be considered a type of pocket pet.

The two living species of chinchilla are Chinchilla chinchilla (formerly known as Chinchilla brevicaudata) and Chinchilla lanigera. C. chinchilla has a shorter tail, a thicker neck and shoulders, and shorter ears than C. lanigera. The former species is currently facing extinction; the latter, though rare, can be found in the wild. Domesticated chinchillas are thought to be of the C. lanigera species.

Chinchillas formerly occupied the coastal regions, hills, and mountains of Chile, Peru, Argentina, and Bolivia. Overexploitation caused the downturn of these populations and, as early as 1914, one scientist claimed that the species was headed for extinction. Five years of fieldwork (published in 2007) in Jujuy Province, Argentina, failed to find a single specimen. Populations in Chile were thought extinct by 1953, but the animal was found to inhabit an area in the Antofagasta Region in the late 1900s and early 2000s. The animal may be extinct in Bolivia and Peru, though one specimen found (in a restaurant in Cerro de Pasco) may hail from a native population.

In their native habitats, chinchillas live in burrows or crevices in rocks. They are agile jumpers and can jump up to 1.8 m (6 ft). Predators in the wild include birds of prey, skunks, felines, snakes and canines. Chinchillas have a variety of defensive tactics, including spraying urine and releasing fur if bitten. In the wild, chinchillas have been observed eating plant leaves, fruits, seeds, and small insects. In nature, chinchillas live in social groups that resemble colonies, but are properly called herds. Herd sizes can range from 14 members up to 100, and herding behavior is thought to promote both social interaction and protection from predators. They can breed any time of the year, though breeding season typically falls between May and November. They are typically monogamous. Their gestation period is 111 days, longer than most rodents. Due to this long pregnancy, chinchillas are born fully furred and with eyes open. Litters are usually small in number, predominantly two.

Both species of chinchilla are currently listed as Endangered by the IUCN Red List of Threatened Species due to a severe population loss approximated at a 90% global population loss since 2001. The severe population decline has been caused by chinchilla hunting by humans. The long tailed-species was listed on the IUCN Red List as "Very rare and believed to be decreasing in numbers" in 1965. From 1982 to 1996, both species were listed as Indeterminate. In 2006, the long-tailed species was listed as "Vulnerable" while the short-tailed species was listed as "Critically Endangered". By 2008, both were listed as "Critically Endangered", and in 2016 they were reclassified as "Endangered" due to limited recovery in some areas.

Chinchilla fur trade on an international level goes back to the 16th century. Their fur is popular due to its extremely soft feel, which is caused by the sprouting of 25 hairs (on average) from each hair follicle. The color is usually very even, which makes it ideal for small garments or the lining of larger ones, though some large pieces can be made entirely from the fur. A single, full-length coat made from chinchilla fur may require as many as 150 pelts, as chinchillas are relatively small. Their use for fur led to the near extinction of one species (C.chinchilla), and put serious pressure on the other (C. lanigera). Though it is illegal to hunt wild chinchillas, they are now on the verge of becoming extinct because of continued poaching. Domesticated chinchillas are still bred for fur.

The domestic chinchilla is descended from Chinchilla lanigera, the long-tailed Chinchilla. They are the more common one in the wild, as the other species, Chinchilla chinchilla, or short-tailed Chinchilla, has been hunted nearly to extinction. Therefore, domestic chinchillas have thinner bodies, longer tails and larger ears. In the wild, the average life-span of a chinchilla is ten years; however, they could live up to 20 years in human care.