Chinchillas are either of two species (Chinchilla chinchilla and Chinchilla lanigera) of crepuscular rodents of the parvorder Caviomorpha. They are slightly larger and more robust than ground squirrels, and are 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 mammals that live on land. Their bodies are covered in 20,000 hairs, with 50 hairs growing from each follicle. In the water, the sea otter has a denser coat. The chinchilla is named after the Chincha people of the Andes, who once wore its dense, velvet-like fur. By the end of the 19th century, chinchillas had become quite rare after being hunted for their ultra-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.