This dissertation addresses the following question: Does the political and economic configuration of the European Union (EU) generate distributive duties amongst EU citizens, and/or between member states? If so, what are these duties and under which conditions do they apply? This dissertation is a contribution to the field of normative political theory, where the problem of distributive justice in the EU remains undertheorized. It is argued that three areas of tension in the present-day EU require normative examination: (1) a discrepancy between the degrees of political integration and social integration in the Union; (2) the existence of legal grounds for shared principles of justice, including the EU Charter of Fundamental Rights, with a contrasting lack of mechanisms to provide and enforce them; and (3) the fact that, under the principle of non-discrimination, EU citizens are entitled to the same set of social rights, but only when they live in the same member state. These tensions have only heightened with the recent economic crisis, which gave rise to conflicting views regarding the desirability and feasibility of a social Europe. What do member states and EU citizens owe to each other? How would a just EU look? This dissertation argues that two key justifications for distributive justice apply to the EU. Firstly, it is argued that, in the EU, coercion and democracy are sufficiently institutionalized to generate redistributive duties. Accordingly, this dissertation contends that responsibilities to redistribute should be shared by the three levels of government – local, national, and supranational. In practice, this means that the EU should act as a safety net for domestic social citizenship, supplementing national welfare systems whenever they fail to fulfil a threshold of basic goods for their citizens. Secondly, it is argued that the current degree of economic integration in the Union generates strong claims of reciprocity amongst member states. The rules of the common market, the single currency, and the free-movement area should then consider not only efficiency-related, but also distributive concerns. Amongst the proposed policies are an EU labour code setting minimum social standards for all EU workers, a minimum corporate tax rate in the EU, and a fund for global competitiveness aimed at improving the competitive position of distressed member states. Therefore, a combination of pre-distributive instruments (e.g. rules of cooperation) and redistributive instruments (e.g. inter-state transfers) is desirable in order to realize social justice in the EU. In addition, this dissertation examines the feasibility conditions of these proposals at great length. It is argued that, in the long-run, distributive justice at the EU level is a feasible project. The proposals mentioned above are tested against four major feasibility requirements: (i) fitting with the political culture of member states, (ii) being economically sustainable, (iii) being translatable into functioning institutions, and (iv) being consistent with the degree of social solidarity amongst EU citizens. The dissertation arrives at the following conclusions. Firstly, since the policy proposals advanced by the dissertation build on an existing “overlapping consensus” on basic social provision, and respect the current diversity of welfare regimes, they fit the political culture of the member states. Secondly, the proposals are economically sustainable because they focus on pre-distribution, leaving only a residual role for redistribution. Thirdly, the policies advocated by the dissertation can be realized through a limited change in the treaties, which may include certain conditionality clauses, and the creation of a European agency for social justice. Finally, given that sufficiency – not equality – is the main value behind the present proposal, the latter is consistent with the limited level of social solidarity in the Union.