This report synthesizes the insights explored within the ERC BlockchainGov reading group on “Legitimacy in Blockchain,” taking place bi-weekly from July 2021 until June 2022. The report investigates the role of legitimacy in blockchain systems from descriptive, conceptual, and normative perspectives. It summarizes the discussions and provides recommendations concerning the role of legitimacy in blockchain systems drawing from the talks held by the reading group. The organizers of the reading group are part of several initiatives, including a five-year-long (2021-2026), EU-funded (ERC grant of €2M) on ‘Blockchain Gov’ at the CNRS (France)/EUI (Italy), a Future Fellowship project funded by the Australian Research Council on ‘Cooperation through Code’ at RMIT (Australia) and the Coalition of Automated Legal Applications (CO-ALA). The “Legitimacy in Blockchain” report is one of a series that includes the “Blockchain Technology, Trust, and Confidence” report (De Filippi et al., 2022) and “Blockchain Technology & Polycentric Gover-nance” report (De Filippi et al., forthcoming).