The guinea pig, also known as the cavy, (Cavia porcellus) is a rodent belonging to the Caviidae family. This species does not exist in the wild any longer. Despite its name the animal is neither related to the pig family, nor originated from Guinea. Domesticated around 5,000 year ago in the Southern America, after European colonization, it is now widely distributed because of its popularity as a pet and a food source. The guinea pig is commonly used in biomedical research, for example in studies of the human immune system, since guinea pig immunological genes are more similar to human than those from mouse. This makes the guinea pig a very important model organism for toxicology and vaccine testing.

The guinea pig genome has 32 chromosomes containing 3.4 Gb with 20,000 protein-coding genes. The reference proteome is derived from the genome sequence submitted in 2008 to the EMBL/GenBank/DDBJ databases.