WASH is an acronym that stands for "water, sanitation and hygiene". It is used widely by non-governmental organizations and aid agencies in developing countries. The purposes of providing access to WASH services include achieving public health gains, improving human dignity in the case of sanitation, implementing the human right to water and sanitation, reducing the burden of collecting drinking water for women, reducing risks of violence against women, improving education and health outcomes at schools and health facilities, and reducing water pollution. Access to WASH services is also an important component of water security. Universal, affordable and sustainable access to WASH is a key issue within international development and is the focus of the first two targets of Sustainable Development Goal 6. Targets 6.1 and 6.2 aim at equitable and accessible water and sanitation for all. In 2017, it was estimated that 2.3 billion people live without basic sanitation facilities and 844 million people live without access to safe and clean drinking water.

Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation systems aim to protect human health by providing a clean environment that will stop the transmission of disease, especially through the fecal–oral route. For example, diarrhea, a main cause of malnutrition and stunted growth in children, can be reduced through adequate sanitation. There are many other diseases which are easily transmitted in communities that have low levels of sanitation, such as ascariasis, cholera, hepatitis, polio, schistosomiasis, and trachoma, to name just a few.