The Sumatran tiger (Panthera tigris sumatrae) is a tiger subspecies that inhabits the Indonesian island of Sumatra and has been classified as critically endangered by IUCN in 2008 as the population is projected at 176 to 271 mature individuals, with no subpopulation having an effective population size larger than 50 individuals, with a declining trend.
The Sumatran tiger is the only surviving member of the Sunda Islands group of tigers that included the now extinct Bali tiger and Javan tiger. Sequences from complete mitochondrial genes of 34 tigers support the hypothesis that Sumatran tigers are diagnostically distinct from mainland populations.