Is there solidarity in Europe? Or is the unification project that began in 1957 doomed to failure by the selfishness of the member states? The Preamble to the Treaty on European Union, the Maastricht Treaty of 1992, refers to the desire of the signatories ‘to deepen the solidarity between their peoples’. Yet the EU’s approaches to the euro crisis and migration have left little of this solidarity. This chapter traces solidarity, both national and international, as a frequent watchword during the twentieth century. The workers and unions movement praised it in the highest terms. The GDR christened its central welfare association ‘Volkssolidarität’ (People’s Solidarity). The West German left pledged its allegiance to ‘anti-imperialist solidarity’ with countries like Vietnam and Nicaragua. Being there for one another, providing mutual help and actively supporting the vulnerable: these are the central pillars of solidarity as it is practised in welfare-state programmes and institutions. People have been striving to build on them since the Weimar Republic. Yet the conditions and limitations of practical solidarity are also under discussion, now more than ever before.