Collectivity: Ontology, Ethics, and Social Justice brings new voices and new approaches to under-developed areas in the philosophical literature on collectives and collective action. The essays in this volume introduce and explore a range of topics that fall under the more general concept of collectivity, including collective ontology, collective action, collective obligation, and collective responsibility. A number of the chapters link collectivity directly to significant issues of social justice. The volume addresses a variety of questions including the ontology and taxonomy of social groups and other collective entities, ethical frameworks for understanding the nature and extent of individual and collective moral obligations, and applications of these conceptual explorations to oppressive social practices like mass incarceration, climate change, and global poverty. The essays draw on a variety of approaches and disciplines, including feminist and continental approaches and work in legal theory and geography, as well as more traditional philosophical contributions.