Called barking deer because of their cry, muntjacs are solitary and nocturnal, and they usually live in areas of thick vegetation. They are native to India, Southeast Asia, and southern China, and some have become established in parts of England and France. Fea's muntjac (M. feae), of Myanmar (Burma) and Thailand, is an endangered species.

Most species of muntjac stand 40–65 cm (15–25 inches) high at the shoulder and weigh 15–35 kg (33–77 pounds). Depending on the species, they range from grayish brown or reddish to dark brown. Males have tusklike upper canine teeth that project from the mouth and can be used to inflict severe injuries. The short antlers have one branch and are borne on long bases from which bony ridges extend onto the face (hence another common name, rib-faced deer); the female has small knobs in place of antlers.

A previously unknown species of muntjac was discovered in the Vu Quang Nature Reserve of northern Vietnam in 1993–94. It was named the giant muntjac because it appears to be larger than other species, with an estimated weight of 40–50 kg.