Moral duties are regularly attributed to groups. In the media or on the street, we might hear that a specific country has a moral duty to defend human rights, that environmentalists have a moral duty to push for global systemic reform, or that the affluent have a moral duty to alleviate poverty. Do such attributions make conceptual sense or are they mere political rhetoric? And what does that imply for the individual members of these groups? Group Duties offers the first comprehensive answer to these questions. Stephanie Collins defends a Tripartite Model of group duties - so-called because it divides groups into three fundamental categories. First, we have combinations - collections of agents that don't have any goals or decision-making procedures in common. These groups cannot bear moral duties. Instead, we should re-cast their purported duties as a series of duties, one held by each agent in the combination. Each duty demands its bearer to "I-reason": to do the best they can, given whatever they happen to believe the others will do. Second, there are groups whose members share goals but lack decision-making procedures. These are coalitions. Coalitions also cannot bear duties, but their alleged duties should be replaced with members' several duties to "we-reason": to do one's part in a particular group pattern of actions, on the presumption that others will do likewise. Third and finally, collectives have group-level procedures for making decisions. They can bear duties. Collectives' duties imply duties for collectives' members to use their role in the collective with a view to the collective doing its duty. With the Tripartite Model in-hand, Collins argues that we can target our political demands at the right entities, in the right way, for the right reasons.