This chapter explores how public opinion intersects with the legitimacy of the European Union in an era marked by overlapping and persistent crises. It traces the shift from an elite-driven conception rooted in “permissive consensus” to a politicized space where integration is actively contested and public support becomes conditional and issue-specific. Successive shocks—financial, migratory, sanitary, and geopolitical—have prompted institutional adaptations, reinforcing patterns of differentiated integration while reshaping the expectations of citizens. The chapter then unpacks the individual-level foundations of EU attitudes, focusing on economic evaluations, political heuristics, ideological orientations, and the interplay between populist narratives and Eurosceptic mobilization. Public opinion now acts as a structuring force: citizens no longer observe integration from the margins, but increasingly interpret, judge, and contest the EU’s role in responding to uncertainty. In this context, EU legitimacy is not granted but earned through visible and coordinated action across diverse national settings.