We investigate if and how imagining a positive future where a societal issue has been rectified can promote hope and support for collective action. Participants imagined (vs. not) a positive future related to climate change (Study 1, N = 301) and economic equality (Study 2, N = 489), two years versus several decades from now. In both studies, imagining a positive future led to support for collective action via increased hope. In Study 1, imagination increased the perceived possibility of achieving the collective goal, in Study 2 it increased its perceived desirability. Possibility was positively related to hope, in particular when imagining a near future, whereas desirability of the collective goal was positively related to hope for a distant imagined future. The research provides evidence for the power of imagination in inspiring hope and collective action, and shows the shifting meaning of hope depending on collective action context and timeframe of the imagination.