Gastroesophageal junction (GEJ) is the interface between the esophagus and the stomach. It is the area which separates these two hollow organs which have different structure and function. The esophagus is a muscular tube which serves as the active conduit for the passage of food while the stomach is saccular and the most dilated part of the fore gut and alimentary tract. This serves the function of receiving ingested food, breaking it down and then releasing it to the duodenum in small aliquots. The esophagus is lined with squamous epithelium while the stomach is lined with columnar epithelium. The tumors involving the GEJ may have their origin in the esophagus, the cardia or the stomach. The stomach and cardia tumors are adenocarcinomas. This chapter covers the classification of GEJ, epidemiology, diagnostic and staging workup, multimodality treatment, esophageal trials relevant to the management of gastroesophageal junction tumors, surgical approach, and stage-wise management.