An information processing system, which includes: an information distribution server; a client apparatus; and a plurality of service providing servers that provide service to a user of the client apparatus, and the information distribution server including: a user authentication information memory that stores user authentication information; a receiving section that receives authentication information from the plurality of service providing servers; and an authentication proxy information distributing section that distributes authentication proxy information prepared based on the user authentication information and the authentication information, and the client apparatus including: a user authentication section that carries out authentication of the user, and an authentication proxy section that, if the authentication is carried out by the user authentication section, executes a proxy authentication when the user accesses at least one of the plurality of service providing servers on the basis of the distributed authentication proxy information.