The Truong Son muntjac or Annamite muntjac is a species of muntjac deer. It is one of the smallest muntjac species, at about 15 kg, half the size of the Indian muntjac (or common muntjac). It was discovered in the Truong Son (Annamite) mountain range in Vietnam in 1997. It was identified by examination of skulls and descriptions provided by villagers, who call it samsoi cacoong, or “the deer that lives in the deep, thick forest.” It lives at elevations of 400–1000 metres, where its small size allows it to move through dense undergrowth.

Found in the Truong Son mountains, it was only discovered in 1997.

It is considered data deficient in terms of deciding its status.