Abstract: The aim of this book is to provide an overview of the relations between the Papacy and various areas of Christendom throughout the twelfth century. Contrary to the traditional historiographical approach, the Papacy is examined here not as an all-powerful institution, but as an “emerging” power. Like the powers that turned to the Apostolic See, the Papacy itself also sought legitimation, within a dynamic process of interaction with the institutions of its time, characterised by advances, setbacks, changes, and continuous negotiation. The reciprocal influences resulting from this process contributed, on the one hand, to the dissemination and consolidation of the Roman Primacy and, on the other, to attempts to establish or consolidate new kingdoms and political entities in twelfth-century world.