The 2019 centenary of the Paris Peace Conference makes for a fitting time to reconsider peacemaking after the Great War. Renewing the conversation between history and international relations theory provides new ways of thinking about the history of international relations. What the book calls sovereignty at the conference revolved around a fundamental effort to redesign the international system itself, the rules under which that system operated, and the kinds of states and empires that were supposed to inhabit it. This book considers not just the Treaty of Versailles with Germany, but all five treaties produced by the conference, as well as the Treaty of Lausanne of 1923 with post-Ottoman Turkey. It considers topics within sovereignty as diverse as the criminalization of Germany and the other defeated Central Powers, the unmixing of lands and peoples in drawing borders, the influence of revolution, and the formation of a new locus of sovereignty in the League of Nations.