Background: The Roma are Europe's largest ethnic minority. Their history has been shaped by marginalization, stigmatization, discrimination, slavery, persecution and murder, and to date, they continue to face prejudice and social exclusion. The Roma population is generally poor, living in crowded and low quality housing in segregated communities on the outskirts of cities, often lacking basic physical infrastructure, including adequate water, sanitation and hygiene (WASH). To better understand the obstacles the Roma are facing, we aimed to review and synthesize available peer-reviewed literature, and identify obstacles to improvement. Methods: We conducted the first systematic review of peer-reviewed literature on water, sanitation and hygiene among Roma communities in Europe, published between 2000 and 2020. A total of 30 publications met the inclusion criteria. We extracted data relating to WASH conditions and services, associated risk factors, exposures and outcomes, examined the role of cultural norms in shaping health behaviors, and obstacles to improvement. Results: Our review shows that across Europe, Roma communities face more challenges than the majority population with respect to access to WASH, waste management and environmental hygiene, appropriate housing and hygienic living environments. Prominent themes in the literature to describe WASH conditions about European Roma populations include limited access, affordability, and quality of WASH services; self-management of WASH as response and adaptive tactic; unsafe WASH as a reason for eviction; and health risks associated with substandard WASH services. The same factors determining the poor quality of WASH services and environmental health impede their improvement. Major barriers to WASH access and affordability among the Roma include discrimination, social exclusion, lack of formal education, poverty, geography, legal and social aspects, and cultural perceptions of health risks, political top-down approaches, lack of political will, and lack of involvement of the Roma community in planning. Besides, Roma are not well represented in national statistics, with data collection being complicated not only by difficulties of access and underfunding, but also by distrust and culturally distinctive health beliefs. Conclusions: The situation and cultural context of WASH among Roma is challenging and complex. Our review demonstrates not only the urgent need for action for Roma communities in particular, but may have broader applicability to ethnic and social minorities in other parts of the world. Future research to overcome obstacles to improvement needs to be inclusive, and involve community members as key informants, with their participation enhancing the reliability of data, contributing to social justice and solidarity, disseminating information, contributing to feasible recommendations and implementation of interventions.