Early oral feeding is the preferred mode of nutrition for surgical patients. Avoidance of any nutritional therapy bears the risk of underfeeding during the postoperative course after major surgery. Considering that malnutrition and underfeeding are risk factors for postoperative complications, nutritional therapy is mandatory for any surgical patient at nutritional risk, especially for those undergoing upper gastrointestinal surgery. The focus of this guideline is to cover nutritional aspects of the Enhanced Recovery After Surgery (ERAS) concept and the special nutritional needs of patients undergoing major surgery, e.g. for cancer, and of those developing severe complications despite best perioperative care. From a metabolic and nutritional point of view, the key aspects of perioperative care include: a) Integration of nutrition into the overall management of the patient, b) avoidance of long periods of preoperative fasting c) re-establishment of oral feeding as early as possible after surgery d) start of nutritional therapy early, as soon as a nutritional risk becomes apparent e) metabolic control e.g. of blood glucose, f) reduction of factors which exacerbate stress-related catabolism or impair gastrointestinal function, g) minimized time on paralytic agents in the postoperative period, and h) early mobilization to facilitate protein synthesis and muscle function. The guideline presents 44 recommendations for clinical practice in patients undergoing elective and non-elective surgery, including new recommendations for frailty assessment, sarcopenia diagnosis, and prehabilitation. As in the former ESPEN practical guideline, the recommendations were additonally presented in decision-making flowcharts.Copyright © 2025 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.