This chapter introduces the foundational framework of a Well Integrity Management System (WIMS), emphasizing the need for a structured, lifecycle-based approach to proactively manage integrity across diverse well portfolios. Unlike isolated technical fixes, WIMS integrates policies, risk assessment, competency, procedures, monitoring, data management, and continuous improvement into a cohesive system. It establishes clear roles, ensures compliance with international standards such as ISO 16530 and NORSOK D-010, and aligns integrity practices with broader Safety Management Systems (SMS). Key components include leadership commitment, hazard identification, operational controls, intervention procedures, and performance monitoring through key performance indicators and audits. The chapter also highlights the importance of robust data systems, cross-functional coordination, and human factors in sustaining WIMS effectiveness. By addressing implementation challenges and leveraging international standards, WIMS transforms well integrity from reactive maintenance into a proactive, risk-informed discipline essential for safe and sustainable operations.