Multi-sided platforms have been increasingly recognized as enablers for circular supply chains. This notwithstanding, scholars are still struggling with a lack of deep understanding of the different roles that multi-sided platforms may play to enable inter-organizational collaborations among supply chain actors to foster the creation of circular supply chains, especially in the business-to-business setting. To address this research gap, the paper develops a taxonomy of multi-sided platforms enabling circular supply chains in the business-to-business setting, by leveraging existing literature as well as an empirical analysis that included 26 multi-sided platforms. Such platforms have been identified through the involvement of a panel of experts into this research area and analysed through a Delphi method. The proposed taxonomy is characterized by two dimensions: (i) the circular supply chain strategy that can be fulfilled through multi-sided platforms, i.e., closing, slowing, or narrowing of resource loops; and ii) the supply chain(s) involved by the resource loops to fulfil such strategies, i.e., either the supply chain in which a resource was originally addressed to or different supply chains. The taxonomy includes six clusters of multi-sided platforms enabling circular supply chains in the business-to-business setting. The study represents the first attempt to provide an overarching conceptualization of the different roles of multi-sided platforms enabling circular supply chains in the business-to-business setting. Furthermore, it informs managers on how multi-sided platforms can be exploited by companies to foster the creation of circular supply chains in this setting.