This book provides a comprehensive overview of the ways in which the concept of collective responsibility is relevant to ongoing normative debates in social and political philosophy. Individual chapters address issues such as the relationship between collective obligations and collective responsibility, the kinds of groups which can be the subjects of collective responsibility and obligations, and the relationship between the obligations of groups and the obligations of individual members of those groups. The book also puts these concepts to work in a number of applied cases, including questions around corporate responsibility and responsibility of AI, or debates about the responsibilities of individuals in relationship to questions about state wrong-doing, or the obligations of allies of marginalised social groups. The guiding principle of the book is that by taking both the theoretical and the applied issues seriously, we can gain new insights into the structure of collective responsibility and its practical implications. In addition to drawing on technical contributions of social ontology, the book is interested in what our real-life practices reveal to us about collective responsibility. The further question is should some of our institutional practices be revised in light of the implicit ontological claims that they make. This book appeals to academics and students in philosophy, political theory and legal studies, especially graduates and postgraduates.