There has been increasing attention to examining informal (i.e., horizontal), rather than formal (i.e., vertical), approaches to leadership over the last several decades, enhancing our understanding of the dynamics of emergent leadership. Although such research has led to a growing comprehension of the process of, and factors involved in, leader emergence, the literature still lacks theoretical coherence. Without a clear way to connect and synthesize extant research, the time is right for a much-needed comprehensive review. To address this issue, we examine emergent leadership research to date with the aim of developing a concise overview and comprehensive framework of the literature. In doing so, we (1) review past conceptualizations, establish a clear, common definition, and compare emergent leadership to other related constructs; (2) review previous operationalizations and provide recommendations for future measurement; (3) develop a comprehensive organizing framework of existing research; and (4) use our organizing framework, as well as three existing theories related to emergent leadership, to generate a series of detailed suggestions for future research for the next decade and beyond.