IntroductionAccess to safe and affordable drinking water, sanitation and hygiene (WASH) for all is needed to safeguard human health, high on societal and political agendas. According to official estimates, populations in high-income countries (HICs) are well served. Vulnerable communities at the margins of rich societies, including people experiencing homelessness, however, are often underserved and overlooked. For them, safe WASH is often a dream rather than reality. To date, no study has been conducted in Germany – one of the countries most affected in Europe. MethodsWe chose a qualitative mixed-method approach to understand WASH (in)security challenges that people experiencing homelessness are facing. Data were collected in Bonn, Germany, from 25 people experiencing homelessness (in-depth interviews, arts-based workshops, group discussions), their service providers (social workers), and (un)available public infrastructure (inspections), in 2023. Data were analyzed following the dimensions of the Human Right to Water and Sanitation (HRTWS): availability; accessibility; affordability; acceptability; quality and safety. ResultsPeople experiencing homelessness largely lack available, accessible, affordable, acceptable and safe WASH. Open urination and defecation are often the only alternative, resulting in substantial health risks and diseases. Women face particular challenges, especially while menstruating. Extreme weather events complicate existing WASH insecurity further, creating additional hardships for unhoused people and their service providers. The missed realization of the HRTWS has far-reaching consequences, making it harder to transition out of homelessness. ConclusionsMuch remains to be done to serve unhoused people in HICs better with WASH. Their experiences shed light on the underlying complexities, and the implications of different often interconnected challenges, including instability, mobility, preexisting diseases, mental health conditions and substance use disorder. Different insecurities exist among different sub-groups (e.g. women, people with limited mobility). They are valuable key informants for targeted health messaging and interventions.