This chapter analyzes the literature on inter- and transregionalism. It elaborates on these concepts and shows how the literature has dealt with three key research questions: the drivers for the emergence of inter- and transregionalism, explanations for their institutional design, and the effects/impact of inter- and transregionalism on the regions and on the global order. The analysis of the literature shows that the phenomena of inter- and transregionalism are underexplored both in empirical and theoretical terms, despite their growing relevance to the global order and to processes of global governance. Key areas addressed are South–South relations, the role of non-state actors in these processes, and the comparison of inter- and transregional governance.