Inflation in fragile states is often treated as a technical macroeconomic problem, yet its consequences are fundamentally political. In South Sudan, hyperinflation has not only disrupted prices but eroded the social foundations of state authority by undermining salaries, savings, contracts, and everyday economic expectations. The concept of inflationary delegitimation captures how monetary collapse weakens the credibility of the state as a minimally protective and reliable authority. Situated within debates on the political economy of inflation, state legitimacy, and fiscal sociology, the manuscript examines how macroeconomic instability translates into political fragility. Focusing on South Sudan, with comparative reference to Zimbabwe, Sudan, and the Democratic Republic of the Congo, the study addresses three interrelated questions: how hyperinflation—reaching over 800% in 2016—undermined state legitimacy through the erosion of civil service pay, collapse of private markets, and reversion to barter and coercive allocation; what causal relationship links war financing through monetary expansion, exchange rate collapse, and the political effects of delegitimation, including defection and armed opposition; and which stabilisation strategies remain viable in conflict-affected contexts characterised by weak tax bases, humanitarian pressures, and constrained fiscal governance. Methodologically, the study combines macroeconomic data analysis using IMF Article IV consultations and National Bureau of Statistics data (2013–2023) with political economy process tracing that links monetary policy decisions to key political developments. It further incorporates comparative analysis of monetary crises in Zimbabwe (2008–2009), Sudan (1990s), and the DRC, alongside interviews with Sou