Historically, the Sumatran Rhino was found across Southeast Asia, including Bhutan, India, China, Myanmar, Cambodia, Thailand, Lao PDR, Indonesia and Vietnam. The exact historic range is uncertain as reports of Rhino occurrence failed to differentiate between the three different Asian Rhino species. Until the 1990s populations continued to rapidly decline, estimated at 50% population loss each decade. The total population of Sumatran Rhino has declined by at least 80% in the past 30 years, arguably making it the most threatened large terrestrial mammal. There is a 90% certainty of the species extinction within the next 60 years.

The largest remaining populations of Sumatran Rhino are found in three protected areas of Sumatra: Bukit Barisan Selatan, Way Kambas and Gunung Leuser National Park. In Bukit Barisan Selatan there are no more than 10 individuals, Way Kambas contains 15-25 individuals and there are approximately 50 individuals in Gunung Leuser National Park.

The Sumatran Rhino resides in tropical and montane moss forests, close to water and in hilly regions. With seasonal flooding of lowland areas, Sumatran Rhino migrate uphill. Although Sumatran Rhino are usually found in primary forest where they rely on salt licks, they have been seen crossing into unprotected secondary forests, in search of water.

The species is generally solitary, except for mating and mothers with calves. Males tend to have larger habitat ranges of 5,000 hectares compared to 1,000-1,500 hectares for females. Although both males and females have made longer treks in search of saltlicks.

The protection of the Sumatran Rhino not only benefits this species but also many other species which share the same habitat. The Sumatran Rhino is considered the most threatened terrestrial mammal on Earth. The last remaining populations represent the last of the species, therefore they are the final hope of saving a species from the brink of extinction.

Although Sumatran Rhinos face different threats depending on their location in Sumatra, a similar threat facing the species is their small population density. This threatens to further reduce population sizes due to difficulties locating breeding partners and problems with inbreeding.

Sumatran Rhinos have been subjected to extreme poaching for their horns, resulting in collapse of populations. Rhino horns have traditionally been used in Chinese medicine. Currently, poaching of Sumatran Rhino is opportunistic and not operating on the same scale as seen for African Rhinos.

Sumatran Rhinos have suffered from habitat loss and fragmentation resulting from human population expansion and human encroachment. There is a threat that in the future with projected human population growth, human encroachment onto protected areas may increase, increasing the human-wildlife conflict.

A Saving The Survivors (STS) team flew to Borneo in 2017 to work on one of the last 3 remaining Sumatran Rhino in Malaysia. This female suffered from a growth on the left side of her face, and the STS team, together with a veterinary dentist from Malaysia funded by STS, assisted with the diagnosis and management of the growth that affected the teeth of this highly endangered Rhino.