From the rise of populist leaders and the threat of democratic backsliding to polarizing culture wars and the return of great power competition, the backlash against the political, economic, and social liberalism 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 societal transformations. 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, and geopolitical. 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.