Besides creating new opportunities and improving the lot of many people around the world, globalisation and economic integration have also generated economic and social losses. The latter are particularly concentrated among the lower and middle classes of advanced industrialised countries, who have seen their position worsen primarily as a consequence of shifts in technological and geographic production patterns. Meanwhile, the nation state’s capacity to tackle social problems such as inequality, poverty and unemployment has been declining as a result of its exposure to capital flows, endogenous transformations like ageing, institutional stickiness and growing public debt burdens. The populist response to this combination of problems is to reverse the process of globalisation and integration, and return to hard national borders. If at all possible, such sovereignist recipes would not, however, be an effective solution to the challenges of globalisation and integration. While such challenges must be acknowledged, new social policy solutions should be devised to improve the lot of the “losers” of globalisation and integration without giving up the many advantages brought about by these processes. We argue that the European Union is the appropriate sphere in which to devise such solutions, for it works at a scale large enough to preserve the gains from openness while constituting an arena for the legitimate and viable creation of new boundaries for market corrections. Based on these premises, we present ideas for the development of a European Social Union, structured on five interrelated components: 1) the Member States’ national social spaces; 2) the social citizenship space: 3) the transnational social space; 4) the EU’s social policy; and 4) the European social constitution