Non-sovereign nations are fragile: not because they lack identity but because their futures depend on sustained collective efforts to preserve institutions, cultures, and political autonomy while they remain unequal partners within constitutional frameworks. In a brilliant sociopolitical analysis of five non-sovereign nations - Catalonia, Northern Ireland, Wallonia, South Tyrol, and Quebec - Félix Mathieu offers new empirical evidence that a state's constitutional character shapes the management of national diversity and advances novel ideas for creating authentic multinational democracies. Beginning with each state's formative rupture and unfolding through the twists of political modernity, Fragile Nations shows how political, social, and economic forces interact with constitutional structures. It examines how unitary or federal states enable or constrain minority nations in building institutions and shaping their destinies. Mathieu brings empirical depth to theoretical debates and takes a compelling look at the democratic principles of pluralism and equity, which can sustain fairer, more inclusive multinational states. Fragile Nation engages in questions about nationalism, federalism, minority nations, and the challenges of governance, enriching wider conversations about identity, sovereignty, and coexistence in diverse societies.