Massive rotator cuff tears (MRCTs) are a complex clinical entity associated with significant pain, functional limitations, and biomechanical disruption of the shoulder joint. This entry comprehensively reviews the epidemiology, natural history, and progression of MRCTs, highlighting critical factors such as age, comorbidities, tear size, and retraction influencing repairability and outcomes. Anatomical and biomechanical considerations, such as MRCTs loss of the force couple, as well as superior migration and anterosuperior escape of the humeral head, are also detailed to contextualize the management goals for shoulder function. Key diagnostic modalities, including advanced imaging and classification systems, are discussed to facilitate accurate assessment and treatment planning. Management of MRCTs spans nonoperative strategies, such as structured physical therapy and injection therapies, to a spectrum of surgical interventions tailored to patient-specific factors and the repairability of the MRCT. For repairable MRCTs, surgical options include open or arthroscopic rotator cuff repair, with possible patch augmentation and anterior cable reconstruction. For irreparable MRCTs, surgical options include debridement and subacromial decompression, partial rotator cuff repairs, tendon transfers, subacromial balloon spacers, tuberoplasty, superior capsular reconstruction, and reverse total shoulder arthroplasty. Each technique is evaluated for its biomechanical rationale, clinical outcomes, and indications, emphasizing the importance of personalized care to optimize function and minimize complications.