An increasing number of studies have suggested the imposition of data access and data sharing obligations for online platforms or gatekeepers. Some of these obligations have been included in the proposed Digital Markets Act and Digital Services Act, which either presuppose or encourage the creation of repositories of information accessible to qualified actors. In parallel, the European Commission is promoting for strategic economic sectors and domains of public interest the concept of common European data spaces, defined as “large pools of data in these sectors and domains, combined with the technical tools and infrastructures necessary to use and exchange data, as well as appropriate governance mechanisms”. However, we are yet to know the rules, procedures and institutional safeguards applicable to these data sharing mechanisms, which are undoubtedly crucial when it comes to determining their legality under competition law. This chapter sketches the challenges involved in this determination for a wide range of collaborations revolving around data access and data sharing, which we call “data collaboratives”.