This stout-bodied rodent weighs up to 6 kg (13 pounds) and has a body length of up to 50 cm (about 20 inches) and a short, bushy tail up to 18 cm long. Thick fur on the upperparts ranges through various shades of brown; the feet are darker and the underparts are buff. Melanistic (nearly black) and Albino individuals occur in some populations. Found from the eastern and central United States northward across Canada and into Alaska, they most commonly live along forest edges abutting meadows, open fields, roads, and streams, but they are occasionally encountered in dense forest. The woodchuck is solitary except in the spring, when a litter of four to six young is born (one to nine have been recorded). The young stay with the mother for two to three months.

Although woodchucks dig deep and extensive burrow systems, they are also good swimmers and can climb tall shrubs and sizable trees. They are most active in the morning and the evening, eating grasses and other green plants as well as some fruit and the bark and buds of trees. They feed heavily in summer and early fall, accumulating huge fat reserves for the winter. The animal is a true hibernator (hibernation). It curls into what appears to be a lifeless ball; its body temperature drops nearly to the ambient temperature of the burrow; and its heart rate decreases from 75 to 4 beats per minute. During the winter months the burrow may also provide shelter for foxes, skunks, opossums, raccoons, and other small animals, particularly cottontail rabbits. Woodchucks were once the objects of sport hunting and are considered quite edible. Classified as a marmot (genus Marmota), the woodchuck is a member of the squirrel family, Sciuridae, within the order Rodentia (rodent).