A B S T R A C TThis article introduces a theoretical framework for conceptualizing public library membership and belonging as an ongoing action net of joint intention and collective action between individual members of the public and the library. It provides an analysis of how membership is constituted, observed, and documented by public libraries from a social-constructivist perspective. Drawing on social theory and philosophy, organizational studies, and secondary public library data sources, a high-level typology of public library member categories from the political and organizational modes of public library action is proposed. Member types are characterized using institutionalized structures of public library use, access, data, discourse, behavior, and social media applications. Implications of this framework for future research and public library innovation are suggested in conclusion."