This book examines the language and the ideology of the Pax Romana, the Pax Britannica and the Pax Americana within the broader contexts of 'hegemony' and 'empire'. It addresses three main themes: a conceptual examination of the way in which hegemony has been justified; a linguistic study of how the notion of pax (usually translated as peace) has been used in ancient and modern times; and a study of the international orders created by Rome and Britain. Using an historiographical approach, the book draws upon texts from Greco-Roman antiquity, and sources from the nineteenth, twentieth and twenty-first centuries to show how the pax ideology has served as a justification for hegemonic foreign policy, and as an intellectual exercise in power projection. From Tacitus' condemnation of what he described as 'creating a wilderness and calling it peace', to debates about the establishment of a Pax Americana in post-Saddam Hussein's Iraq, the book shows not only how the governing elite in each of the three hegemonic orders prescribed to a loose interpretation of the pax ideology, but also how their internal disagreements and different conceptualisations of pax have affected the process of 'empire-building'. This book will be of interest to students of international history, empire, and International Relations in general.