With a focus on the African Union, this chapter examines the Security Council’s practices when interacting with regional organisations in collaborative peace operations. The Security Council plays a critical role in two ways: (i) it identifies security threats and the required responses, and it authorises UN missions to deal with them; and (ii) it determines the role, if any, to be played by regional organisations and authorises the action they can take to address threats to peace in their regions. Africa is both the site of conflicts that have necessitated UN peace operations or the Council’s authorisation of enforcement actions, as in Libya in 2011, and home to that regional organisation which has engaged the most with the United Nations in maintaining international peace and security. The overarching argument of this chapter is that – notwithstanding changes in the post-Cold-War international political landscape and the rise of other voices from the periphery – the status of the Security Council as custodian of the collective security system remains undiminished. Its centrality and primacy have not been challenged or usurped by the African Union or other regional organisations.