Sumatran rhinos are the smallest of the living rhinoceroses and the only Asian rhino with two horns. They are covered with long hair and are more closely related to the extinct woolly rhinos than any of the other rhino species alive today. Calves are born with a dense covering that turns reddish-brown in young adults and becomes sparse, bristly and almost black in older animals. Sumatran rhinos compete with the Javan rhino for the unenviable title of most threatened rhino species. While surviving in possibly greater numbers than the Javan rhino, Sumatran rhinos are more threatened due to habitat loss and fragmentation. The remaining animals survive in small, fragmented non-viable populations, and with limited possibilities to find each other to breed, its population decline continues. Just two captive females have reproduced in the last 15 years.

The Sumatran rhino once roamed as far away as the foothills of the Eastern Himalayas in Bhutan and eastern India, through Myanmar, Thailand, possibly to Vietnam and China, and south through the Malay Peninsula. Today, the species only survives on the Indonesian islands of Sumatra and Borneo. Experts believe the third subspecies is probably extinct.