Fibrous dysplasia is a benign condition but can lead to severe long-bone deformities. Three-dimensional (3D) printing technology is a rapidly developing field that has now been popularized to aid surgeons in preoperative planning. We report a case of hip deformity in a 21-year-old woman who suffered from fibrous dysplasia and underwent a corrective osteotomy. We utilized open-source 3D computing software for preoperative planning before producing an osteotomy guide to aid in the operation.