The ability of individuals and groups to identify, assess, and pursue alternative possible futures is an essential component of their ability to deliberately and collectively respond to major sustainability challenges rather than experience unguided or forced change. Deliberately engaging in transformation processes inevitably requires imagination. We refer to imagination for transformations as interdependent cognitive and social processes that create representations of present and possible future states of the world that can inform public deliberation, policy, decision making, and behavior from the individual to the global scale. We contend that imagination is an essential capacity for securing ecological, social, economic, and cultural well-being in times of rapid and often unpredictable global change. We sketch an emerging interdisciplinary research agenda on imagination as a transformational capacity and its role in transformation processes, building on contributions to a special issue on this subject. We specifically focus on imagination in relationship to transformative agency, causation, and individual-collective dynamics. Our aim is to identify research questions and challenges that are most pressing with a view to supporting efforts of transformations toward sustainability.