Abstract Global governance institutions emerge around problems ranging from climate change to cybersecurity. Expert knowledge is instrumental in defining these problems, developing corresponding solutions, and thereby structuring international order. But in the process of problem construction, claims to expertise are competing, often contingent, and increasingly rely on graphs and models, black-boxing normative assumptions of knowledge production. Thus, international relations (IR) requires an approach that engages with the political dynamics of knowledge production happening within and beyond the spheres of traditional politics. This special forum on objects of expertise offers such an approach, and this introductory article lays out the overarching framework. It conceptualizes objects of expertise as authoritative knowledge relevant for governing put into a socio-material form. First, understanding expertise in terms of authoritative knowledge points to the contested attempts at rendering knowledge authoritative in a specific sphere; expertise is a relational category of (contested) group belonging. Second, knowledge becomes expertise when it is made authoritative in relation to a problem relevant for governing. Finally, expertise gains objectual character when it is put into a delineable socio-material entity in which it assumes a recognizable, specific form. This form grants objects of expertise a certain level of credibility and stability, allowing them to function as trusted sources of information and guidance.