We examined the epidemiology, clinical manifestations, histopathology, management, and outcomes of gastrointestinal basidiobolomycosis, an uncommon manifestation of infection caused by the fungus Basidiobolus ranarum. In this retrospective observational cohort study, cases of gastrointestinal basidiobolomycosis in the United States were identified by reviewing medical records from Mayo Clinic Hospital (Phoenix, AZ) and contacting local infectious diseases specialists, pathologists, gastroenterologists, the Arizona Department of Health Services, health departments of adjacent states, the Armed Forces Institute of Pathology, and the US Centers for Disease Control and Prevention. A comprehensive literature review identified additional cases worldwide. Of 44 patients (mean age, 37 years [range, 2-81 years]) with gastrointestinal basidiobolomycosis, most were from the United States (19 patients [43%], of whom 17 [89%] were from Arizona) or Saudi Arabia (11 [25%]). Most (28 [64%]) were previously healthy. Common chronic medical conditions among 15 patients (34%) were diabetes mellitus (8 patients [18%]) and gastric disorders (7 [16%]). Common findings were abdominal pain (37 patients [84%]) and a palpable abdominal mass (19 [43%]). Intraabdominal malignancy was the leading provisional diagnosis (19 patients [43%]). The large bowel was involved in 36 (82%), the small intestine in 16 (36%), and the liver or gallbladder in 13 (30%). Characteristic histopathologic findings were observed in 43 (98%). Eight patients (18%) died. Combined surgical intervention and antifungal therapy was the preferred treatment. Gastrointestinal basidiobolomycosis is an emerging invasive fungal infection in desert regions of the US Southwest. Clinical findings mimic malignancy and inflammatory bowel disease. Surgical excision and prolonged antifungal therapy are associated with favorable outcomes.