Also known as the Sunda Sambar, the Javan rusa natively occurs on the islands of Java, Bali and Timor in Indonesia. 

It has been introduced to Irian Jaya, Borneo, the Lesser Sunda Islands, Maluku, Sulawesi, Pohnpei, Mauritius, Réunion, Fiji, Tonga, Samoa, Vanuatu, the Solomon Islands, the Christmas Island, the Cocos Islands, Nauru, Mainland Australia, New Caledonia, New Zealand, Papua New Guinea, New Britain, and New Ireland. The Javan rusa was introduced by the Dutch to New Guinea in the early 1900s.

While its population in many of these places is large, its population in its home range is only around 10,000, having declined significantly in the last 20 years, which has resulted in it being protected in Indonesian law, and it being listed as vulnerable. Unfortunately a number of places like Baluran National Park, is has been overtaken by thorny acacia, which has killed of this species in the areas where this has happened.

Generally, a nocturnal animal, it can occasionally be seen grazing during the day. Usually keeping out of sight, and keeping in small groups. The main predators of the Javan rusa includes Javan leopard, Sunda clouded leopard, dhole, estuarine crocodile, reticulated python, and Komodo dragon on the islands of Rinca, Komodo, and Flores.

In their native range, they are considered as vulnerable to extinction. However, given the recent decades decline in this species, it is quite possible that this conservation status will get worse in the last few years.

Seven subspecies of the Javan rusa are recognised:

• R. t. timorensis (Timor rusa deer) – Timor.
• R. t. djonga – Muna and Butung Islands.
• R. t. floresiensis (Flores rusa deer) – Flores and other islands.
• R. t. macassaricus (Celebes rusa deer) – Sulawesi.
• R. t. moluccensis (Moluccan rusa deer) – Maluku Islands.
• R. t. renschi – Bali.
• R. t. russa (Javan rusa deer) – Java.