This article synthesizes the literature on citizenship and immigration to evaluate the heft of citizenship and theorize why it matters. We examine why citizenship laws vary cross‐nationally and why some immigrants acquire citizenship while others do not. We consider how citizenship influences rights, identities, and participation and the mechanisms by which citizenship could influence lives. We consider frameworks, such as cultural and performative citizenship, that de‐center legal status and the nation‐state. Ultimately, we argue for a claims‐making approach to citizenship, one that is a relational process of recognition, includes actors outside the individual/state dyad, and focuses on claims to legitimate membership.