Gorham–Stout disease (GSD) is a rare angiomatous disorder characterized by osteolysis. We report the case of a 66-year-old woman who developed sudden left eye proptosis and facial pain. Neuroimaging demonstrated a destructive mass involving the roof and lateral wall of the left orbit with adjacent abnormal orbital soft tissue. An initial biopsy of the soft tissue was nondiagnostic; however, transcranial biopsy of the orbital roof revealed an intraosseous cavernous angioma, with infiltration of orbital fat by angiomatous tissue. Despite resection of the orbital roof and lateral wall, the orbital lesion continued to expand, leading to signs of a compressive optic neuropathy. The patient then reported severe back pain, prompting imaging that demonstrated disseminated bony involvement of the axial skeleton, eventually leading to the diagnosis of GSD. The patient was treated with a bisphosphonate and a vascular endothelial growth factor inhibitor with stabilization of disease.