Upper gastrointestinal bleeding (UGIB) is among the most common causes of hospital admissions worldwide with an incidence of 50–150 per 100,000 patients annually. Mortality rates have decreased over the past decade, but rapid diagnosis and treatment remain critical for improved patient prognosis. UGIB can be a manifestation of an array of pathologies that arise proximal to the ligament of Treitz, and clinical presentation varies based on the degree of bleeding. In general, slow and small quantity bleeding may manifest as melena or hematemesis, whereas large volume and more rapid bleeding may present as hematemesis or hematochezia. Recent management and prognosis of UGIB have improved with the emergence of advanced endoscopic techniques, patient optimization strategies, and widespread use of proton pump inhibitors. Technique selection should be individually tailored to the etiology of UGIB and clinical considerations. This chapter will highlight the most common etiologies of nonvariceal and variceal UGIB (VUGIB) and their respective preferred endoscopic treatment methods.