The Virginia Opossum (Didelphis virginiana), commonly known as the North American Opossum, is the only marsupial found in North America north of the Rio Grande. A solitary and nocturnal animal about the size of a domestic cat, it is a successful opportunist and is found throughout Central America and North America east of the Rockies from Costa Rica to southern Ontario (it was also introduced to California in 1910, and now occupies much of the Pacific coast); it seems to be still expanding its range northward. Its ancestors evolved in South America, but were enabled to invade North America in the Great American Interchange by the formation of the Isthmus of Panama about 3 million years ago. It is often seen near towns, rummaging through garbage cans, or lying by the side of the road, a victim of traffic.

The Virginia Opossum is the original animal named "opossum". The word comes from Algonquian 'wapathemwa' meaning "white animal", not from Greek or Latin, so the plural is opossums. Colloquially, the Virginia Opossum is frequently called simply possum. The name is applied more generally to any of the other marsupials of the Didelphimorphia and Paucituberculata orders, which includes a number of opossum species in South America.

A very large Virginia Opossum baring its sharp teeth and lips, making it appear quite vicious. It is the largest member of its genus, family and order and is the largest of the opossums. They are typically 15–20 inches (38–51 cm) long and weigh between 9 and 13 pounds (4–6 kg). Their coats are a dull grayish brown, other than on their faces, which are white. Opossums have long, hairless, prehensile tails, which can be used to grab branches and carry small objects. They also have hairless ears and a long, flat nose. Opossums have 50 teeth and opposable, clawless thumbs on their rear limbs. Opossums have thirteen nipples, arranged in a circle of twelve with one in the middle.

An Virginia opossum female may have as many as 25 babies, but she usually will have between seven to eight. The reason opossums have so many babies to insure that some of them survive. Like most marsupials, opossums are very small when they are born - about the size of a navy bean. Opossums have thirteen nipples, arranged in a circle of twelve with one in the middle. The babies climb up the mother's fur and into her pouch where they find a teat. Some babies will not find their way to the pouch and will die. If they make it to the pouch, only babies who find one of the thirteen teats will survive. They will stay in the pouch and suckle for 55-60 days. Then they will move out of the pouch and spend another four to six weeks on their mother's back. In some parts of their range, females will have three litters a year.

Opossum carry diseases such as leptospirosis, tuberculosis, relapsing fever, tularemia, spotted fever, toxoplasmosis, coccidiosis, trichomoniasis, and Chagas disease. They may also be infested with fleas, ticks, mites, and lice. Opossum are hosts for cat and dog fleas, especially in urban environments.            To deter opossums an array of chemical products is marketed for repelling various wildlife species but, unfortunately, none offer significant results. The odor of mothballs or naphthalene crystals, used as a home remedy repellent, has occasionally been reported to be successful in driving opossum from confined areas, but can build up toxicity in the soil. There are no registered toxicants for poisoning opossum. Poison baits sold for the control of rodents should never be used in an attempt to control opossum, skunks, or raccoons. The penalty for such pesticide misuse can be substantial and the practice usually becomes known as a result of the accidental poisoning of someone's pet.