Contemporary socio-economic transformations in South Asia are creating increasingly serious water problems (scarcity, flooding, pollution) and conflicts. Conflicts over water distribution, water-derived benefits, and risks often play out along axes of social differentiation like caste, wealth, and gender. Those with least power, rights, and voice suffer lack of access, exclusion, dispossession, and further marginalisation, resulting in livelihood insecurity or increased vulnerability to risks. In this paper we propose analysing these problems as problems of justice – problems of distribution, recognition, and political participation. Drawing on wider environmental justice approaches, a specific water justice focus needs to include both the specific characteristics of water as a resource and the access, rights, and equity dimensions of its control. We argue that recognising water problems as problems of justice requires a re-politicisation of water, as mainstream approaches to water resources, water governance, and legislation tend to normalise or naturalise their – basically political – distributional assumptions and implications. An interdisciplinary approach that sees water as simultaneously natural (material) and social is important here. We illustrate these conceptual and theoretical suggestions with evidence from India.