The Water, Sanitation, and Hygiene (WASH) Insecurity Analysis is based on the human right to water and sanitation. WASH insecurity is influenced by WASH service levels but also by exposure to natural or human-induced hazards and underlying vulnerabilities, such as gender or poverty. WASH insecurity results in negative WASH-related outcomes (e.g., increased rates of water and sanitation diseases) and ultimately, a denial of people’s human rights to water and sanitation. The WASH Insecurity Analysis identifies geographic areas and quantifies the population at risk of WASH insecurity and the population already experiencing WASH insecurity. It is a tool and a process that can bring together diverse stakeholders across the humanitarian-to-development continuum, including those working in the nexus space or fragile contexts, and promotes localization by providing analytical insights at the local level before and aftershocks. It can be used by governments and development actors to prioritize sectoral investments.