From the rise of populist leaders and the threat of democratic backsliding to the rejection of open markets and the return of great power competition, the backlash against the political, economic, and social status quo is increasingly labeled "illiberal." Yet, despite the increasing importance of these phenomena, scholars still lack a firm grasp on "illiberalism" as a conceptual tool for understanding contemporary trends. The Oxford Handbook of Illiberalism addresses this gap by establishing a theoretical foundation for the study of illiberalism and showcasing state-of-the-art research on this phenomenon in its varied scripts-political, economic, cultural, geopolitical, and civilizational. To do so, the Handbook is organized in eight parts. The first develops the concept of illiberalism by delineating it from other "isms," such as conservatism and authoritarianism. The second highlights the historical and contemporary entanglements between illiberalism and liberalism. The third explores how illiberalism intersects with various political and social identities, such as religion and gender. The fourth examines the political economy of illiberalism. The fifth unpacks the presence of illiberalism in regimes and countries around the world, including Brazil, China, Hungary, India, Poland, Russia, South Africa, and Turkey. The sixth identifies how illiberalism manifests in international relations. The seventh analyzes grassroots expressions of illiberalism. And the eighth probes the theoretical foundations of illiberal thought, linking it to conservatism, postliberalism, and religious doctrines. Bringing together the expertise of dozens of scholars, The Oxford Handbook of Illiberalism offers a thorough overview that characterizes the current state of the field and charts a path forward for future scholarship on this critical and quickly developing concept.