How does civil society engage in climate governance and how do we understand the range of forms and tactics? This chapter presents a history of civil society involvement in climate change policymaking, discussing the diversity of actors involved and the insider and outsider tactics that they take. First, we provide a summary of the literature on civil society participation in climate governance, paying particular attention to the diversity of actors and actions. Second, building off of recent events that involve both insider and outsider tactics, we review the role that civil society has played as outsiders during international climate negotiations. Third and finally, we conclude by discussing the likely role that civil society will play as the climate regime continues to try to reduce greenhouse gas emissions around the world.