This chapter offers a comprehensive analysis of well integrity challenges throughout the complete lifecycle of a well, from initial design and construction to intervention and final abandonment. The chapter begins by defining lifecycle-based well integrity and identifying key touchpoints—critical phases where decisions, failures, or stressors impact long-term containment and structural performance. Using field examples and case histories, this chapter explores how mechanical, chemical, and operational loads evolve with time, affecting the performance of well barrier elements such as casing, cement, packers, and valves. Each lifecycle stage is examined in detail as follows: