The past few decades saw the transformation of Hong Kong from a liberal enclave to a revolutionary crucible at China's offshore. The Making of Leaderful Mobilization takes you through the evolution of protests in this restive city, where ordinary citizens gradually emerged as the protagonists of contention in place of social movement organizations. The book presents a theory of mediated threat that illuminates how threat perceptions fueled shifting forms of mobilization - from brokered mobilization where organizations played guiding roles to leaderful mobilization driven by peer collaboration among the masses. Bringing together event analysis, opinion polls, interviews, and social media data, this book provides a thorough and methodical anatomy of Hong Kong's contentious politics. It unveils the processes and mechanisms of collective action that likely prevailed in many contemporary social movements worldwide. Our temporal approach also uncovers the multiple pathways reshaping hybrid regimes, underscoring their resilience and fragility.