Efforts to engage new actors in political decision-making through innovative participatory programs have exploded around the world in the past 25 years. This trend, called participatory governance, involves state-sanctioned institutional processes that allow citizens to exercise voice and vote in public policy decisions that produce real changes in citizens' lives. Billions of dollars are spent supporting these efforts around the world. The concept, which harks back to theorists such as Jean-Jacques Rousseau and John Stuart Mill, has only recently become prominent in theories about democracy. After presenting the foundational research on participatory governance, the essay notes that newer research on this issues falls into three areas: (i) the broader impact of these experiments; (ii) new forms of engagement, with a focus on representation, deliberation, and intermediation; and (iii) scaling up and diffusion. The essay concludes with a research agenda for future work on this topic.