The Water Supply, Sanitation and Hygiene (WASH) Poverty Diagnostic in the West Bank and Gaza is part of a global initiative to improve evidence on the linkages between WASH, poverty, and service delivery at the local level. The Diagnostic explores long-term trends in access to improved water and sanitation, assesses how equitably water supply and sanitation services are distributed across regions and by household wealth, brings new evidence on the transition from Millennium Development Goal (MDG) to Sustainable Development Goal (SDG) indicators, and examines the binding constraints to improve service delivery. While the global initiative also looks at the linkages of WASH services with other sectors such as health and education, data limitations made this impossible in the context of West Bank and Gaza. However, this Diagnostic gives special attention to water scarcity, which is a major constraint to viable service delivery. West Bank and Gaza is a very water-scarce lower-middle-income territory with a relatively water dependent economy and is vulnerable within its geopolitical setting. Assuring water security is thus a priority. Water security requires adequate water resources that are well managed, including management of risks, and water services that provide sustainable, efficient, and equitable.