Can institutional agency be understood in terms of informal (plural) group agency? This book argues that the answer is ‘yes’, and more specifically that both can be understood ultimately in terms of the agency of individuals who are members of such groups and in terms of the concepts already at play in our understanding of individual agency. Thus, the book argues for a strong form of methodological individualism. It is the second part of a two-part project that extends the multiple agents account of plural agency in From Individual to Plural Agency (OUP 2016) to institutional agency. It argues that the key to understanding institutional agency is recognizing that the time-indexed institutional membership relation is socially constructed in the sense that it is a special type of status function, a status role, which is accepted by the agent who fills the role. The book analyzes constitutive rules in terms of essentially intentional patterns of collective action and status functions in terms of constitutive rules and conventions. It analyzes institutions as structures of interrelated status roles that can be successively occupied by different agents, and provides a reductive account of institutional action in terms of these roles and the notion of proxy agency, in which one agent or group acts through another who is authorized to act for them. The account is applied to both corporations and nation states.