Musk deer can refer to any one, or all seven, of the species that make up Moschus, the only extant genus of the family Moschidae. Despite being commonly called deer, they are not true deer belonging to the family Cervidae, but rather their family is closely related to Bovidae, the group that contains antelopes, bovines, sheep, and goats. The musk deer family differs from cervids, or true deer, by lacking antlers and preorbital glands also, possessing only a single pair of teats, a gallbladder, a caudal gland, a pair of canine tusks and—of particular economic importance to humans—a musk gland.

Musk deer live mainly in forested and alpine scrub habitats in the mountains of South Asia, notably the Himalayas. Moschids, the proper term when referring to this type of deer rather than one/multiple species of musk deer, are entirely Asian in their present distribution, being extinct in Europe where the earliest musk deer are known to have existed from Oligocene deposits.