Cavia is a genus in the subfamily Caviinae that contains the rodents commonly known as guinea pigs. The best-known species in this genus is the domestic guinea pig, Cavia porcellus, an important meat animal in South America and a common household pet outside of South America.
Cavia is classified in order Rodentia, although there was a minority belief in the scientific community that evidence from mitochondrial DNA and proteins suggested the Hystricognathi might belong to a different evolutionary offshoot, and therefore a different order. If so, this would be an example of convergent evolution. Other scientists were critical of this hypothesis. This uncertainty is largely of historical interest, as abundant molecular genetic evidence now conclusively supports classification of Cavia as rodents  (and references therein). This evidence includes draft genome sequences of Cavia porcellus and several other rodents (available on-line ).