The Skinny pig or skinny is an almost hairless strain of guinea pig. Skinny pigs typically have hair on their muzzles, feet, and legs, but are hairless over the remainder of their bodies. Some of them have a thin covering of fuzzy hair on their backs as well. The Skinny pig is not one of the 13 recognized cavy breeds by the American Cavy Breeders Association. A healthy skinny has skin that is mostly smooth, with some wrinkling around the legs and neck. The body is full with no appearance of spine or ribs. Skinnies can come in a variety of skin colors and patterns, including "Dutch", "Brindle", and "Himalayan". The term "skinny" is used for hairless guinea pigs either because it colloquially refers to the exposed skin of the animal, or because it describes their thinner appearance due to their lack of hair.

The guinea pig or domestic guinea pig, also known as the cavy or domestic cavy, is a species of rodent belonging to the genus Cavia in the family Caviidae. Breeders tend to use the name "cavy" for the animal, but "guinea pig" is more commonly used in scientific and laboratory contexts. Despite their name, guinea pigs are not native to Guinea, nor are they closely related to pigs. They originated in the Andes region of South America. Studies based on biochemistry and hybridization suggest they are domesticated animals that do not exist naturally in the wild, descendants of a closely related cavy species such as C. tschudii. They were originally domesticated as livestock for a source of meat, and are still consumed in some parts of the world.