Cornish hen or Cornish chicken, breed of poultry that originated in Cornwall, England, but gained prominence only after it was established in the United States. Its body shape is quite different from that of other chickens. Both males and females have short legs and broad muscular breasts. Although relatively slow-growing, the Cornish hen has excellent meat qualities and is used extensively in breeding programs today. Its cross with the fast-growing Plymouth Rock chicken is responsible for most of the broiler and frier types currently on the market. An increasingly popular form of Cornish poultry, marketed for its delicious meat, is the Rock Cornish game hen. This is actually a standard meat-type chicken packaged at a smaller size.