While International Relations scholars have recently excavated a number of systems previously unstudied by the discipline, few have discussed the emergence of fully-fledged systems in prehistory. Fully-fledged system have continuous multilinear (between more than two units at the time) and multidimensional (more than one institution in evidence) interaction at its core. Drawing mainly on extant archaeological research, we examine the European Bronze Age. We find that Indo-European in-migrating herders during the third millennium BCE established patron-led polities based on the steppe practices of the clients’ oath to his patron and the patron’s feast. A third practice, the guest/host relationships between patrons, anchored Europe’s first regional inter-polity systems. We also find that, due to an increase in interaction capacity caused by better boat building, horse-transport and the emergence of new technologies that made possible warfare at a distance, there systems were harbingers of a European-wide system of what we call Central Site Polities. We conclude that European inter-polity systems hail from the Bronze Age and suggest that the practices on which these systems rested are still, mutatis mutanda, with us. Further work on possible genealogical ties between the Central Site System and subsequent European systems awaits.