The use of rigorous sociological methods to study the social transformations brought about by the emergence of the European Union (EU) constitutes the core of the 'sociology of the EU'. This sub-disciplinary field draws on concepts such as European identity, transnational fields, Europeanisation and social integration. The aim of this chapter is to offer an overview, necessarily selective, of the contributions of sociological analyses of the EU, and to propose perspectives for future research. We focus primarily on empirical sociology, based on qualitative or quantitative studies, rather than on social theory which, because of its broad ambition, goes beyond the realm of EU studies proper. The chapter first defines what is sociology of the EU and outlines its historical development and the early debates it faced. It then looks at the main contributions of sociology to EU studies, before looking at it the other way around and delving into the main contribution of EU studies to classical sociology such as historical sociology, sociology of elites or sociology of public action.