Therapeutic endoscopy has evolved from a predominantly diagnostic discipline into a core modality for managing conditions historically treated with surgery. This chapter reviews current evidence and technical principles across motility disorders, reflux disease, obesity, early neoplasia, strictures, and pancreaticobiliary pathology, highlighting how endoscopic therapies now provide definitive, organ-preserving alternatives. Third-space endoscopy enables precise myotomy for esophageal, gastric, and pharyngoesophageal disorders with clinical outcomes equivalent or superior to surgical approaches, along with shorter recovery and lower perioperative risk. Parallel advances in incisionless antireflux interventions and a growing suite of endoscopic bariatric and metabolic procedures expand access to durable physiologic modification for patients who are ineligible for or prefer to avoid surgery. Endoscopic resection techniques, including endoscopic mucosal resection and submucosal dissection, allow curative treatment of early gastrointestinal neoplasia while avoiding the morbidity associated with oncologic operations. Endoscopy has also become the preferred approach for managing postoperative complications, anatomic and benign strictures, leaks, and complex pancreaticobiliary disease, achieving high rates of clinical success with fewer adverse events than operative or percutaneous techniques. The chapter underscores the importance of patient selection, anatomical assessment, and multidisciplinary collaboration, which remain central to optimizing outcomes as these modalities expand. With continued innovation, including hybrid approaches, next-generation devices, artificial intelligence, and robotic platforms, therapeutic endoscopy is positioned to further reshape surgical care. Understanding the capabilities, limitations, and practical applications of these techniques is essential for clinicians, practicing at the intersection of endoscopy and minimally invasive surgery.