This paper discusses the cooperative potential of the great power system in post-Napoleonic Europe – the Pentarchy – and argues that the predominant policies of peacekeeping and “balance of power” as well as the short period of regular diplomatic congresses after 1815 point towards an early form of European integration. It thereby challenges the prevalent narrative of the process of European unification as a unique development that only began after World War II. The possibilities for and tendencies towards inter-state cooperation andsupranational governance within the framework of the Pentarchy are shown by examining three of its successive core characteristics: firstly, a general understanding to avoid bellicose conflicts to keep the peace and ensure political stability during the monarchist restoration; secondly, a highly dynamic balance of power policy to facilitate peacekeeping and to counter hegemonic ambitions of any great power; and thirdly, the institutionalised format of the Congress system to jointly resolve European affairs and balance great powerinterests during regular meetings. Based on diplomatic documents and treaties as well as the observations of statesmen, politicians and political commentators, the analysis shows how the Pentarchy created spaces for increased cooperation between European states and conservative governments with concurrent interests. Consequently, the paper dismisses the topos of the nineteenth century as the era of the isolated nation-state and argues that the Pentarchy system functioned as a precursor of modern European integration.