West Sumba Regency (Indonesian: Kabupaten Sumba Barat) is a regency in East Nusa Tenggara Province of Indonesia. Established in 1958, the regency was considerably reduced in 2007 with the creation of new Regencies on Sumba Island. Its area is now 709.9 km2, and its population was 111,993 at the 2010 census; the latest official estimate (at January 2014) was 120,162. It has its seat (capital) in (Kota) Waikabubak.
The region is rather dry. One of the main problems for people living in rural areas in the province is frequent shortages of water. Although there are some local supplies of water from wells and springs, water from these sources often becomes scarce during the long dry seasons. In some villages local non-government organisations, some supported with international assistance, support small projects to improve village water supplies.