Invoking the notion of ‘cosmopolitics’ from Bruno Latour and Isabelle Stengers, this volume shows how and why cities constitute privileged sites for studying the search for and composition of common worlds of cohabitation. A cosmopolitical approach to the city focuses on the multiple assemblages of human and nonhuman actors that constitute urban common worlds, and on the conflicts and compromises that arise among different ways of assembling the city. It brings into view how urban worlds are always in the process of being subtly transformed, destabilized, decentred, questioned, criticized, or even destroyed. As such, it opens up novel questions as to the gradual and contested composition of urban life, thereby forcing us to pay more explicit attention to the politics of urban assemblages. Focusing on changing sanitation infrastructures and practices, emerging forms of urban activism, processes of economic restructuring, transformations of the built environment, changing politics of expert-based urban planning, as well as novel practices for navigating the urban everyday, the contributions gathered in this volume explore different conceptual and empirical configurations of urban cosmopolitics: agencements, assemblies, atmospheres. Taken together, the volume thus aims at introducing and specifying a novel research program for rethinking urban studies and politics, in ways that remain sensitive to the multiple agencies, materialities, concerns and publics that constitute any urban situation.