Crises are historical moments of surprise, compressed time, decision and choice. They are turning points that disrupt established orders, goals and expectations, driving leaders to respond defensively or by innovation to protect or extend regimes. Crises involve critical junctures for rulers and ruled, testing their efficiency and legitimacy. They can be judged by the extent to which such threats to existing governance are addressed, whether by deepening integration or by disintegration. Applying this approach comparatively to regionalism in Europe and Asia involves recognising that crises, like regions, come in different types. Economic crises like the 1997-1998 one that threatened Asian prosperity and the one that threatened the euro in 2010-2013 can fruitfully be com­ pared for their effects on integration, but reveal more diversity than simil­ arity. Security, energy, environmental or climatic crises threaten the two regions differently. The chapter acknowledges that diversity, but concentrates on economic and security crises in both regions to get a purchase on whether and how they have driven deeper integration. It begins by surveying social science theories of crisis, selecting out some key ideas and distinguishing between critical moments characterised by extreme threat and longer term inno­ vative transitions. Separate sections examine contexts and comparisons and then the playing out of shorter and longer term recent crises in Europe and Asia, particularly in the economic and security issues and how these have affected their regional integration. They are compared synopti­ cally in the chapter’s conclusion.