Zero Trust Architecture (ZTA) is a cybersecurity framework built on the principle of "never trust, always verify" — eliminating implicit trust within networks and instead requiring continuous verification of every user, device, and transaction regardless of location. Formalized by NIST SP 800-207 in 2020, Zero Trust shifts security from perimeter-based defenses to identity-centric, context-aware access controls, assuming breach as the default state and enforcing least privilege at every layer. In 2026, with 81% of organizations actively adopting Zero Trust to combat ransomware, insider threats, and cloud vulnerabilities, understanding its core principles—verify explicitly, use least privilege access, and assume breach—becomes essential for securing modern hybrid IT environments where traditional castle-and-moat approaches have proven obsolete.