The relationship between democracy and sustainability is a contentious one. Yet diverse groups of citizens need to be engaged in the design and implementation of policies and actions across all scales and sectors for them to succeed and be socially acceptable. But how? From protest and mobilisation to participation in policy and the creation of new spaces of citizen engagement through citizens’ assemblies and the like, governments, businesses, cities and civil society actors are all grappling with the challenge of how best to engage citizens in addressing a series of threats to global sustainability but with uneven capacity to do so. In terms of transforming the democratic state, the chapter engages with the literature on ecological democracy and explores the idea that deepening democracy would extend to democratic control over the economy for the common good. In practice, this might imply expanded spaces and scope for deliberation over plural pathways to sustainability and the use of deliberative and inclusive policymaking processes such as standing panels of citizens, regular polling, multi-criteria mapping and citizens’ assemblies and juries. To really deepen democracy and open the state up would mean including issues of core state interest that are currently off limits for debate and not just what are dismissively termed ‘low-political’ issues.