This chapter analyses the presence, the origins and the potential of co-evolutionary perspectives in planning theory. Co-evolution is conceptualized in different manners in the landscape of planning theory and the wider setting of social theories. The various versions of co-evolutionary theory differ in the elements they focus on, in what is seen as the overall structure, and in the way in which interrelations between systems, and between structures and elements are understood. Spatial planning, as the coordination of policies and practices regarding the organization of space, as spatial governance, is firmly embedded in governance as such. For Evolutionary Governance Theory (EGT) planning systems are configurations of actors and institutions involved in the organization of space. They include evolving discourses about what and how to plan. EGT distinguishes between three sets of dependencies: path dependencies, interdependencies and goal dependencies.