The partnership between the African Union (AU) and the United Nations (UN) is arguably the most institutionalized case of strategic cooperation for contemporary international peacekeeping. While built upon the pursuit of complementarity, the AU-UN partnership often presents conflict. This inter-institutional relationship has primarily been analysed through technical difficulties in peace operational settings. As a result, our understanding remains limited of how the partnership dynamics relate to broader normative struggles of peacekeeping agents. Building on this, the article adopts a less explored legitimacy perspective and ultimately argues that the complex inter-institutional dynamics are constructed in the legitimation struggles of peacekeeping agents. Based on discourse analysis of strategic documents, the article examines legitimation struggles in three main areas of conflictual discourse in the AU-UN partnership - normative grounds for authority, institutional capacity, and doctrines and principles. Additionally, it highlights the complexity of the partnership dynamics that involve an interplay of concurrent practices of self-legitimation, mutual legitimation, and de-legitimation. By doing so, the article importantly contributes to the understanding of how partnership and legitimation work in contemporary international peacekeeping, as well as the relationship between them.
