This prospective, randomized, assessor-blinded clinical trial aims to compare the postoperative analgesic efficacy of ultrasound-guided Erector Spinae Plane Block (ESPB) and Modified External Oblique Intercostal Plane Block (EOIPB) in patients undergoing elective open nephrectomy under general anesthesia. Sixty adult patients will be randomized to receive either ESPB or EOIPB before surgical incision. All participants will receive standardized general anesthesia and postoperative multimodal analgesia. Postoperative pain scores, opioid consumption, rescue analgesic requirements, and postoperative nausea and vomiting will be assessed during the first 24 hours after surgery. The study aims to determine whether one fascial plane block technique provides superior postoperative pain control and recovery following open nephrectomy.