The Treaty of Lausanne (1923) was the definitive diplomatic settlement that legally codified the dissolution of the Ottoman Empire and established the modern post-Ottoman order. This volume moves beyond a Eurocentric narrative to analyse Lausanne as a global inflection point—a framework in which the core dilemmas of the twentieth century were starkly revealed: sovereignty and territorial integrity versus minority rights, the implementation of nationalist homogenisation through compulsory population exchange (regulated under a separate convention), and the tensions between imperial decline and emergent national identity. Through a multiarchival, holistic analysis, it examines how the Treaty codified post-Ottoman sovereignty, structured minority protection, and shaped both regional and global order. Integrating national and international perspectives, the contributors demonstrate how Lausanne’s legal provisions, humanitarian consequences, and economic arrangements not only reshaped Greek-Turkish relations and the Middle East but also reverberated across the international system, influencing the diplomatic strategies of powers from Japan to the Balkans. This collection positions Lausanne not as a final settlement but as a formative origin for the century’s ongoing struggles over regional stability and the meaning of statehood in international law, thereby opening a critical discussion of what constitutes diplomatic success.