Sumba is an island in eastern Indonesia, is one of the Lesser Sunda Islands, and is in the province of East Nusa Tenggara. To the northwest of Sumba is Sumbawa, to the northeast, across the Sumba Strait (Selat Sumba), is Flores, to the east, across the Savu Sea, is Timor, and to the south, across part of the Indian Ocean, is Australia.
The landscape is low, limestone hills, rather than the steep volcanoes of many Indonesian islands. Due to its distinctive flora and fauna Sumba has been categorised by the World Wildlife Fund as the Sumba deciduous forests eco-region. Sumba is within the Wallacea ecozone, having a mixture of plants and animals of Asian and Australasian origin. Most of the island was originally covered in deciduous monsoon forest while the south-facing slopes, which remain moist during the dry season, were evergreen rainforest.