Abstract Introduction Mucormycosis is a rare, opportunistic infection commonly associated with diabetes mellitus, acidosis, neutropenia, organ transplantation, high-dose glucocorticoid therapy, iron overload syndromes, and hematologic malignancy. Case Invasive infection usually presents with rhino-orbital-cerebral (34%), cutaneous (22%), and pulmonary (20%) manifestations. Cutaneous cases are almost always precipitated by trauma or wounds. Only 6 previous cases of cutaneous mucormycosis (Mucor, Rhizopus, Lichtheimia, and others) infection of the breast have been reported in the literature. We herein report a woman with fatal submammary mucormycosis. Report A 45-year-old diabetic woman with alcohol use disorder was admitted from her basement living quarters with septic shock and lactic acidosis. During her intensive care unit stay, she developed worsening eschar of left submammary region. Cultures revealed Rhizopus species and surgical resection revealed invasive hyphae classic for mucormycosis. Despite treatment with liposomal amphotericin and complete resection, the patient died. Discussion Rhizopus infection complicated sepsis-related lactic acidosis and preexisting submammary intertrigoseveral days after admission. This case emphasizes the importance of a continued thorough physical examination that includes visualization of intertriginous areas, including those in submammary areas in septic patients in the critical care unit.