An authentication system includes an authentication server that has a first processor and authenticates a user who uses a terminal to which a login request for a network system has been transmitted, and a first terminal that has a second processor and is used by a user who is not permitted to log in to the network system, in which the first processor is configured to permit the first terminal to log in to the network system in a case where the first terminal is capable of being verified to be located in a specific space where a user who is permitted to log in to the network system is locatable in response to a login request from the first terminal.