Any American marsupial of the genera Didelphys and Chironectes. The common species of the United States is Didelphys Virginiana.
- Any of various nocturnal, usually arboreal marsupials of the family Didelphidae, especially Didelphis marsupialis of the Western Hemisphere, having a thick coat of hair, a long snout, and a long prehensile tail. See Regional Note at possum.
- Any of several similar marsupials of Australia belonging to the family Phalangeridae.