How to change the world? Those concerned about the dangerous drift of global development are asking this question with increasing urgency. Dominant institutions have proved too timorous or too venal for meeting the environmental and social challenges of our time. Instead, an adequate response requires us to imagine the awakening of a new social actor: a coordinated global citizens movement (GCM) struggling on all fronts toward a just and sustainable planetary civilization. Existing civil society campaigns remain fragmented and therefore powerless to leverage holistic transformation. To create an alternative vision and effective strategy for realizing it, consciousness and action must rise to the level of a GCM. We propose a new organizing campaign with the explicit aim of catalyzing this historic agency. This effort would expand and diversify in a “widening circle,” adapting to changing circumstances as it evolves. From the onset, such a project must foster a politics of trust, committed to balancing unity and pluralism on the road to our common future.