Single Sign-On (SSO) is a key aspect of contemporary authentication that improves security as well as efficiency. By allowing users to log in once and access various applications, it lessens password fatigue and eliminates security threats caused by credential reuse. Organizations are helped by enhanced compliance, unified user management, and lower IT support expenses related to password reset. Nevertheless, since SSO consolidates authentication, it also offers a single point of failure. To enhance security, companies must adopt **Multi-Factor Authentication (MFA)**, **session timeouts**, **continuous monitoring**, and **adaptive authentication** to identify and block unauthorized access. An SSO system that is well-secured maximizes both user experience and cybersecurity.