Nutritional morbidity is prevalent in patients undergoing pelvic surgery and associated with poor surgical and oncological outcomes. This chapter will highlight the anatomic and biological bases for nutritional complications in the pelvic surgical patient. We will review clinical evidence for the development, consequences, and potential mitigation of malnutrition. The genitourinary and distal gastrointestinal tracts lie in proximity to the pelvis, and disease in one system often directly impacts the other. Patients with disease in either system are prone to preoperative malnutrition if they develop obstructive symptoms, fistulae, or cachexia. Many will require bowel resection, bypass, or diversion of the fecal stream with an ileostomy or colostomy. The need for adjuvant therapy can exacerbate preexisting malnutrition. Basic and translational studies have uncovered the impact of the intestinal microbiome on outcomes for pelvic surgical patients. More recently, targeted interventions such as nutritional prehabilitation have proven effective at improving outcomes.