This chapter provides a general introduction to the European Commission, the main executive body of the European Union (EU). It argues that it is more productive to compare the Commission to national executives or to a government than to a secretariat of a traditional international organization. It begins with a summary of the Commission’s functions within the EU’s policy process. It then considers the question of Commission influence and autonomy, before moving on to look at the structure, demography, and decision behaviour within the organization—that is, at the role of the President of the Commission and the Commissioners, at the Commissioners’ personal staffs, and at the Commission administration. It then examines the committees and administrative networks that link the Commission to national administrations and interest groups, and also deals with the recent growth of EU agencies. The chapter concludes by emphasizing that the Commission is much more of a European(ized) and supranational institution than it was at its inception.