Collective transformative agency is increasingly becoming a focal point of research and debate in response to acute societal challenges. This book offers a much-needed dialectical perspective on wilful collective actions situated within complex and evolving systems of activity. Annalisa Sannino presents a cutting-edge conceptualization of the collective determination for change toward equity and sustainability, grounded in rich empirical studies that reveal its emergence as a process and how it can be fostered. Advancing cultural-historical scholarship on human activities, the text introduces the novel theory of Transformative Agency by Double Stimulation, offering new ways to rethink research and consolidating long-term partnerships with civil society. The author also contributes an approach to transformative agency that can be mobilized in transdisciplinary dialogues across scientific fields and domains of practice. It is a vital resource for anyone committed to understanding and enacting collective change. This book is also available Open Access on Cambridge Core.