This evidence paper looks at 10 areas identified collaboratively with the United Nations Children’s Fund (UNICEF) on which WASH can plausibly have a strong impact: diarrhoea, nutrition, complementary food hygiene, female psychosocial stress, violence, maternal and newborn health, menstrual hygiene management, school attendance, oral vaccine performance, and neglected tropical diseases. Together, these areas cover the most significant sector outcomes associated with the distinct life course phases that UNICEF seeks to help to address through its WASH activities. UNICEF’s strategic vision on WASH is to achieve universal and sustainable water and sanitation services and the promotion of hygiene, with a focus on reducing inequalities especially for the most vulnerable children, wherever they are; both in times of stability and crisis.