The past 75 years have seen the development of a rule-based system of global governance that plays a frontline role in fighting transboundary problems. The expectations on global governance to deliver have never been higher, but this system also appears more contested than ever before, potentially signaling a crisis of legitimacy. This chapter explores these dual features of contestation and legitimacy in global governance. It shows that contestation occurs through a variety of state and societal actors calling for reform, replacement, or rejection of international organizations. Yet a review of recent data on the popular legitimacy of international organizations shows little evidence of a broad-based legitimacy crisis. The chapter concludes that that contestation does not appear to be in opposition to legitimacy in global governance. Instead, contestation may be seen as a natural component of a dynamic political system of global governance, open to criticism and debate.