Musk deer can refer to any one of, or all seven species, that make up Moschus, the only genus of the family Moschidae. Musk deer are more primitive than cervids, or true deer, because they lack antlers and facial glands, and possess only a single pair of teats, a gall bladder, a caudal gland, a pair of tusk-like teeth and—of particular economic importance to humans—a musk gland. As is implied by their classification under the order Artiodactyla, they are artiodactyls.

Musk deer live mainly in forested and alpine scrub habitats in the mountains of southern 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.