Cliodynamics is a transdisciplinary area of research integrating historical macrosociology, cultural and social evolution, economic history/cliometrics, mathematical modeling of long-term social processes, and the construction and analysis of historical databases. Cliodynamics: The Journal of Quantitative History and Cultural Evolution is an international, peer-reviewed, open-access journal that publishes original articles advancing the state of theoretical knowledge in this transdisciplinary area. In the broadest sense, this theoretical knowledge includes general principles that explain the functioning, dynamics, and evolution of historical societies and specific models, usually formulated as mathematical equations or computer algorithms. Cliodynamics also has empirical content that deals with discovering general historical patterns, determining empirical adequacy of key assumptions made by models, and testing theoretical predictions with data from actual historical societies. A mature, or ‘developed theory’ thus integrates models with data; the main goal of Cliodynamics is to facilitate progress towards such theory in history and cultural evolution.