Social solidarity is a concept with a long history in political thought, entailing networks of relationships that presuppose dependency, reciprocity and responsibility among the members of a group or a political community. Yet solidarity is not charity or a gift, but an institutionalised system of rules and conventions that apply to risk and misfortune. Since solidarity has been historically institutionalised in the context of national states, transnational solidarity has largely remained a utopian project as well as an insufficiently developed principle in the EU legal system. In this chapter we explore individual support for European solidarity as it becomes manifest in distinct ‘solidarities’ across borders such as mutual help in case of natural disaster, financial assistance in the context of economic crisis or solidarity as a governing principle of European integration. Drawing on classical sociological arguments and transactionalist theory, we analyse the extent to which social interactions among Europeans and transnational practices contribute to the formation of solidarity ties in the EU. We show that individual transnational practices, such as tourism, residency in another EU country, transnational friendships or virtual connections with other European societies have a selective role in enabling European solidarities. Rather than a question of cumulative transnational experiences, European solidarity is built on meaningful social connections such as close and diverse transnational friendships.