Sanitation systems are the most vital provisions in a city. Today, however, the global sanitation crisis is urbanizing, and growing numbers of city residents live with the struggle and consequences of not having safe, reliable facilities. While there is a large and vibrant literature on sanitation and cities, we have yet to account for the specifically urban nature of the deepening sanitation crisis in the global South. This article sets out a framework for understanding the dimensions of the urban sanitation crisis through a relational approach comprising five areas: people, life, things, spaces and distributions. Drawing on literature and research on urban sanitation in the global South, the author argues that if research, policy and practice is to better understand and respond to challenges of urban sanitation poverty, an expansive conception of its specifically urban dimensions is crucial.I am grateful to the editors and anonymous reviewers for their constructive comments. The writing of this article was completed with the help of a European Research Council Consolidator Grant, DenCity 773209.Development and Change 50(5):