The Biafran agitation represents a critical lens through which Nigeria’s struggle with ethnic identity, national unity, and federal legitimacy can be examined. Rooted in colonial legacies and exacerbated by post-independence politics, the agitation underscores the paradox of the “One Nigeria” mantra, which simultaneously promotes unity and conceals deep-seated grievances. While existing scholarship has explored federalism, ethnic politics, and separatist movements, little attention has been given to “One Nigeria” as a deliberate political instrument deployed by elites to manage dissent and reinforce legitimacy. This study addresses that gap by interrogating the interplay of identity, ethnicity, and prebendal politics within Nigeria’s federal system. Using historical analysis and theoretical framing through federalism and consociationalism, the research examines how the mantra functions as both a symbolic device and a rhetorical cover for structural contradictions. Findings highlight the persistence of ethnic favoritism, prebendal politics, and exclusionary governance, which undermine democratic consolidation and perpetuate separatist sentiments. The study indicates that the “One Nigeria” discourse, while institutionally embedded, often fails to translate into substantive inclusion, thereby fueling renewed agitation such as the resurgence of IPOB. The significance lies in reframing “One Nigeria” not merely as a slogan but as a contested political strategy, revealing its limitations in fostering genuine unity. This analysis contributes to debates on nation-building, suggesting that reconciliation and equitable governance are essential for sustaining Nigeria’s federal project.