Computer-implemented methods and systems are provided for blockchain-mediated user authentication. Consistent with disclosed embodiments, authentication may comprise operations including receiving, from a user system, an authentication request for a user. The operations may also include determining a root system for the user using a blockchain, and redirecting the user system to the root system. The operations may include receiving, following redirection, a verification message indicating that the root system successfully authenticated the user, and including an authorization code for receiving, from the root system, a root system secret. The operations may include receiving from a database, identification data using the root system secret. Determining the root system may comprise identifying, using the authentication request and index information stored in the blockchain, a block of the blockchain storing root system information for the user. Receiving the identification data may comprise retrieving identification data from the database.