A 21-year-old man presented to the emergency department with rigors and right-eye pain and swelling 3 days after an assault. His temperature was 39.0°C, and his heart rate was 116 beats per minute. Findings on examination of the right eye included tense swelling and dusky discoloration of the eyelid (Panel A), a visual acuity limited to counting fingers, an afferent pupillary defect, an intraocular pressure of 52 mm Hg (reference range, 10 to 21), and markedly limited extraocular movements. A maxillofacial computed tomographic scan showed orbital fat stranding, proptosis, and stretching of the optic nerve, findings suggestive of orbital compartment syndrome. He underwent immediate surgical débridement; the intraoperative findings indicated orbital necrotizing fasciitis (Panel B), and the wound cultures grew group A streptococcus. Orbital necrotizing fasciitis is rare but may result in vision loss and even death. Early recognition is necessary to facilitate timely surgical débridement and appropriate antibiotic therapy. The patient underwent three additional débridements of the right upper eyelid and received a 2-week course of antibiotics and topical medication to lower the intraocular pressure. Two weeks after the initial presentation, he underwent successful skin grafting of the right upper eyelid. At 2 weeks of follow-up, his visual acuity had recovered completely, and at follow-up 6 months later, he continued to have good vision.