This chapter reviews the political science research on European Union (EU) State aid policy. The literature focuses primarily on the evolution of State aid control and on the institutions and actors who play a role in the policy. Resting on Treaty provisions that were little used in the first decades of the European Community, the Commission's incremental soft law approach, supportive jurisprudence from the Court of Justice of the European Union (CJEU), and the involvement private complainants have helped bring together Commission and Member State interests in support of State aid control. The Commission's handling of the financial crisis, a test for the more mature regime, has been largely judged a success. Over time policy initiatives have helped to reduce and target national subsidies, and the enforcement of and compliance with the Treaty provisions have improved dramatically since the late 1980s. The political dimension of the policy seems to have less resonance these days, as there are fewer high-profile controversial cases than in the past, but there are still interesting questions to be addressed about the way in which competition, regional, environmental, cultural and industrial policies are balanced against each other in the design and application of the EU-level policy and decision-making, and what the implications of UK's departure from the EU and the emergence of populist governments and leaders in the Member States might mean for State aid control.