Single Sign-On (SSO) is an authentication method allowing users to access multiple applications or services with one set of login credentials rather than separate logins for each system. After authenticating once, users can seamlessly access connected applications without re-entering passwords. SSO improves user experience by reducing password fatigue and login friction while potentially improving security by reducing the number of passwords users must remember and manage. Government organizations use SSO to allow staff access to multiple internal systems and to provide citizens convenient access to related government services. SSO implementations use protocols like SAML, OAuth, or OpenID Connect to securely share authentication between systems.