In republican political philosophy, citizenship is a status that is constituted by one’s participation in the public life of the polity. In its traditional formulation, republican citizenship is an exclusionary and hierarchical way of defining a polity’s membership, because the domain of activity that qualifies as participating in the polity’s public life is highly restricted. I argue that Black American abolitionist Frederick Douglass advances a radically inclusive conception of republican citizenship by articulating a deeply capacious account of what it means to participate in the public life of the polity. On Douglass’s conception of republican citizenship, what it means to contribute to the polity, and thereby be a citizen, is to act in ways that contest and shape what the polity values. We contest and shape what the polity values not only through public discourse traditionally conceived or grand political acts like revolt, but also through quotidian forms of social interaction. In his pre-American Civil War political thought, Douglass deployed his radically inclusive account of republican citizenship as the conceptual foundation of his stance that enslaved and nominally free Black Americans were already, in the 1850s, American citizens whom the polity ought to acknowledge as such. The everyday resistance in which enslaved Black Americans engaged—their plantation politics—is, for Douglass, a paradigmatic type of citizenship-constituting activity, because it involves modes of collaboration and confrontation that enact a recognition of mutual vulnerability and embody the assertion that one matters. Douglass’s conception of republican citizenship offers a normative framework for emancipatory struggles that strive to secure meaningful membership for the marginalized through the transformation of unjust polities.