The 1923 Treaty of Lausanne, which established the modern Republic of Turkey, represents a pivotal moment of post-Ottoman settlement by legally consolidating political, territorial, and diplomatic outcomes that had already been shaped by military conflict, nationalist mobilization, and prior international agreements. This chapter argues that France played a central and evolving diplomatic role throughout this process, transitioning from a colonial partitioner to a pragmatic mediator operating within shifting power asymmetries and international constraints. Initially committed to the imperial designs of the Sykes-Picot Agreement and the punitive Treaty of Sèvres, France’s costly war against Turkish nationalists in Cilicia prompted a dramatic strategic reassessment rather than a purely normative change of policy orientation. The 1921 Franklin-Bouillon Agreement, a separate peace with Ankara, marked this critical shift, making France the first major Allied power to engage with the Turkish National Movement and signaling an early acknowledgment of the limits of imperial enforcement. At the Lausanne Conference, France subsequently prioritized its economic interests—especially the servicing of the Ottoman Public Debt and the protection of concessions—and acted as a moderating force between a rigid Britain and a resurgent Turkey without exercising decisive control over the final settlement. By abandoning territorial claims and war reparations in favor of a stable bilateral relationship, French diplomacy contributed to, rather than singularly determined, the emergence of a durable peace, securing its financial and cultural stakes in the region while participating in a broader multilateral process that facilitated Turkey’s reintegration into the international system.