Guinea pigs are hystricomorph rodents (related to chinchillas and porcupines) that originated from the Andes Mountains region of South America. Before the colonisation of the Americas by Europeans, the Incas had first begun to domesticate cavies as both religious icons and as a source of food from around 500 BC. In many villages in Peru, Ecuador and Bolivia cavies are still kept today as a source of food. Fed on scraps and becoming food themselves when plump enough, as this mountainous region has little space available for the raising of cattle. As many as 7 million guinea pigs are eaten each year in Peru.

However, they were not bred by the Incas only for food. In Peru guinea pigs have a hallowed place in native folklore. Legend holds that guinea pigs are mystical beings that can heal the sick and assist the dying in the journey from the world of the living to the great beyond.

In the 16th century Dutch explorers introduced guinea pigs to Europe , and selective breeding and captive rearing began in earnest.

Guinea pigs are very popular pets because of their availability, docile temperaments, tendency not to bite or scratch when handled, and relatively clean habits. They are not long-lived, which can be disconcerting to owners (especially children). Many parents, however, believe that having their children experience the relatively short period of companionship and subsequent death is a meaningful way to expose children to the "ups and downs" of life.

Guinea pigs are mammals which belong to the rodent family having large incisor teeth that are continually growing necessitating gnawing to prevent the teeth from overgrowing. The word 'rodent' is derived from the latin word 'rodere' which means 'to gnaw'.

In their natural habitat, guinea pigs live in open, grassy areas. They seek shelter in naturally protected areas or burrows deserted by other animals. Guinea pigs are sociable animals and tend to live in groups. They are strictly herbivorous (plant-eating) and do most of their foraging for grasses, roots, fruits and seeds in the late afternoon and early evening.

Guinea pigs have also played a very important role in the field of medical research, and although most pet lovers today may cringe at the thought of animals being used in laboratory research the the historic and important contribution of guinea pigs to science cannot be overlooked. Guinea pigs are often used as a metaphor for any subject of scientific experimentation (e.g."human guinea pigs"), and this idea persists even though guinea pigs are no longer commonly used as modern experimental animals, as rats and mice (which breed quicker) have replaced them.

In 1890 the antitoxin for diphtheria was discovered using guinea pigs in the research, and as a result the lives of millions of children have been saved. The guinea pig's wide variety of hair types and colors have also made them a prime choice for studies of genetics and heredity. During the 20th century a special strain of smooth-coated white guinea pigs called Duncan-Hartley were bred specifically for laboratory work.