In a world where perimeters have dissolved, Zero Trust is essential for securing cloud-native environments. This guide breaks down the core principles of Zero Trust—Never Trust, Always Verify; Assume Breach; Least Privilege—and applies them to the realities of dynamic infrastructure, microservices, APIs, and multi-cloud complexity. It offers practical tools, implementation strategies, and cultural considerations to help DevSecOps teams and security leaders build resilient systems from the inside out.