Collaborative governance is promoted globally as a potential solution to resource dilemmas and institutional collective action problems. To date, most collaborative governance research has focused on simple partnerships studied in isolation from the broader complex policy systems in which they are embedded. This chapter argues that the analysis of collaborative governance must be expanded to the context of complex polycentric systems where diverse networks of stakeholders participate in an ecology of games involving interlinked collective action problems. We first review what existing research tells us about collaborative governance and simple partnerships, including the relationship to environmental outcomes. We then summarize the emerging research on how principles of collaborative governance can be expanded into the context of complex governance systems.