World-systems analysis (WSA) emerged in the 1960s and 1970s in response to methodological nationalism, ahistoricism, and Cold War–era polemics. It is a whole-systems, historically focused, transdisciplinary, and critical approach whose founding scholars include Immanuel Wallerstein, Samir Amin, Giovanni Arrighi, and Andre Gunder Frank. Key early insights regarding development and underdevelopment are reviewed along with the systemic processes that have been identified including core/periphery differentiation and exploitation. Cyclical processes include economic rise/decline, hegemony/rivalry, and labor/capital domination. Secular trends include geographic expansion, mechanization, and commodification. Three revisionist positions are identified: comparative world-systems, world-system history, and world-systems geopolitics. Ongoing world-systems research on inequality, commodity chains, social movements, the environment, world-systems incorporation, trade patterns, gender, family relations, population movements, urbanization, and geographic networks is introduced. World-systems literatures exist in anthropology, archaeology, geography, history, political science, and sociology. Going forward, areas for further development include better integrating agency into WSA, and considerations of world-system conflict.