- a large, South American, aquatic rodent, Myocastor (or Myopotamus) coypus, yielding the fur nutria.
- an aquatic South American hystricomorph rodent, Myocastor coypus, introduced into Europe: family Capromyidae. It resembles a small beaver with a ratlike tail and is bred in captivity for its soft grey underfur
- the fur of this animal
