This article investigates the interactions between three regional organizationsthe G5 Sahel, the Economic Community of West African States (ECOWAS) and the African Unionin the context of the Sahelian conflict. It argues that these organizations struggle for recognition by the international community and by their member states as the most legitimate regional security actor in the management of the conflict. By focusing on the politics driving these organizations' interactions, this article makes two contributions. First, it complements and expands the literature on regional security governance by showing how these regional organizations are driven by legitimation struggles framed through spatial imaginaries. Each organization delineates a specific space of interventionthe Sahel, West Africa, the Sahelo-Saharato present itself as the right scale of governance. Second, identifying these spatial imaginaries enables a better understanding of African responses to the conflict in the Sahel, and provides insights into the reordering of (West) African security governance and, more broadly, the emergence of new modalities of security governance.