The nutria or coypu is a large, herbivorous, semiaquatic rodent from South America.
Classified for a long time as the only member of the family Myocastoridae, Myocastor is now included within Echimyidae, the family of the spiny rats.
The nutria lives in burrows alongside stretches of water and feeds on river plant stems. Originally native to subtropical and temperate South America, it has since been introduced to North America, Europe, Asia, and Africa, primarily by fur farmers. Although it is still hunted and trapped for its fur in some regions, its destructive burrowing and feeding habits often bring it into conflict with humans, and it is considered an invasive species. Nutria also transmit various diseases to humans and animals, mainly through water contamination.