This dissertation explores the rise of the Young Ottoman movement in the 1860s as a product of the new geopolitical order that emerged in the wake of the Crimean War (1853–1856). It combines a close study of the writings of three major Young Ottoman thinkers with archival research documenting the transnational sources of their ideas, and situates the emergence of these ideas within the histories of both European liberalism and modern Islamic political thought. Chapter 1 (“A Nation in Search of Sovereignty”) charts the profound shift undergone by Ottoman sovereignty over the course of the nineteenth century. It describes the model of sovereignty developed by Tanzimat-era statesmen in conjunction with their European collaborators as porous, a structure reflective of the increasingly internationalized distribution of power over the lives of Ottoman subjects. The Young Ottoman movement, I argue, was an organized response to this newly porous model of sovereignty that resisted both the loss of international prestige and the reduced political efficacy of Ottoman subjects it created; yet the movement itself arose through transnational networks that paralleled the web of formal institutions it sought to challenge, marking a newly internationalized phase of Ottoman dissident activity. The ensuing chapters collectively explore the elaboration of Young Ottoman thought through the writings of three of its leading thinkers—Namık Kemal (1840–1888), Teodor Kasap (1835–1897), and Ali Suavi (1839–1878)—with a focus on the international sources of these thinkers’ conceptions of Ottoman nationhood, political legitimacy and justice. Chapter 2 (“Namık Kemal and the Dream of a Liberal Ottoman Imperium”) presents a reading of the political writings and career of Namık Kemal organized around the themes of hamiyet (zeal), hürriyet (liberty), and hakimiyet (sovereignty) that I argue are foundational to his political thought. In Chapter 3 (“Teodor Kasap and the Making of an Ottomanist Public”), I turn to Namık Kemal’s friend and collaborator, the Greek Ottoman journalist Teodor Kasap. I highlight Kasap’s pivot role as both a shaper and a popularizer of the Young Ottoman conception of nationhood. My exploration of this important but neglected figure focuses on the transnational origins of his cosmopolitan patriotism, tracing the influence of the early years he spent fighting for Italian unification alongside the French novelist Alexandre Dumas on his later career as a champion of the Ottomanist cause. In Chapter 4 (“Ali Suavi and the Ottomanist Critique of Liberalism”), I focus on the life and career of the Islamic scholar Ali Suavi to challenge the widespread characterization of the Young Ottoman movement as fundamentally aligned with European liberalism. I argue that Ali Suavi’s close connections with European conservative thinkers place him within the broader anti-liberal tradition of nineteenth-century thought, even as his writings demonstrate his allegiance to the democratic and populist orientation of his fellow Young Ottomans. My conclusion suggests that Young Ottoman ideas of nationhood and legitimacy were influential in shaping both the regnant ideology of Sultan Abdülhamid II (1876–1909) and that of his opponents, the Young Turks, as well as serving as a crucial link between the liberal patriotic movements that remade southern Europe in the first half of the nineteenth century and the Islamic internationalism that emerged as an important vector of anti-imperialist militancy at that century’s end.