The European Union is a single political and economic supranational community of 27 member states. The process of European integration and enlargement throughout history has been influenced by a number of factors. The European Coal and Steel Community was first established to prevent further armed conflicts in the post - World War II period. In the following period, two more supranational communities were established: the European Economic Community and the European Atomic Energy Community (EUROATOM). Today's European Union was officially established with the entry into force of the Maastricht Treaty on 1 November 1993. The legal nature of the European Union is difficult to define. Since it is the only organization of its kind, in the past many international legal theorists have tried to determine its legal entity. In a series of attempts to define its legal nature, the only category in which we can classify the European Union is sui generis (unique) organization. The fundamental values and objectives of the European Union, such as the promotion of peace, equality, freedom, democracy, the rule of law and human rights, are the main drivers of the functioning of its institutions, the participation of the Member States and all its inhabitants. The aim of this paper is to present and analyze the historical development of the European Union, what the European Union represents today and how the integration process encompassed almost the entire European continent.