As of 2025, 85% of the world population lives in countries typically associated with the Global South. Fifty percent of the world’s population is under age 30. This article introduces the special issue on “Young Adult Life Courses in the Global South.” It aims to provide a conceptual entry point for globally comparative research on young adult life courses. We systematize and contextualize key insights from the twelve contributions to this special issue, which were selected through an open call, on 1) relevant macro-structural conditions for young adult life courses in the Global South, 2) conceptualizing adulthood processes, including implications for young adults’ agency. Based on the contributions to this special issue, we propose a comparative framework that focuses on the locally specific interplay between economic, normative, and temporal conditions for navigating social adulthood. Second, we summarize the authors’ critiques of established concepts of young adulthood and highlight alternative conceptualizations that they employ, including their implications for young adults’ agency. We close by outlining avenues for future research for a globally comparative research agenda on young adult life courses.