Much scholarly work has already examined the causes of “Brexit”, the departure of Britain from the European Union. The main question addressed in the current chapter, by contrast, is: what has the Brexit referendum, and Britain's subsequent drawn-out exit, meant for the EU? Has Brexit required concerted remedial action by the Union's supranational political actors, member states, and political parties? Or have operations just carried on largely as before, only with 27 member states rather than 28? In trying to disentangle the Brexit effect from many other effects on the EU since 2016, I employ a simple counterfactual approach. Given what we know about the preferences of the actors within the EU and of successive British governments, the chapter asks whether it is likely that much would have been different had Britain still been a member when the coronavirus pandemic and the war in Ukraine unfolded. Thereafter, it addresses the development of public opinion and political-party behaviour throughout Europe in relation to membership of the EU. The general conclusion is that, far from impeding European integration, Brexit has contributed to its acceleration. However, the future remains uncertain. It is not inevitable that this integrative effect will endure.