The review of the literature determines that large osteomas of the mandible are relatively rare. We present a case of a 60-year-old man with painless swelling of the left submandibular area and mild difficulty in breathing. The patient complained that the mass have been progressing slowly for at least 20 years. Radiographic studies showed a giant osteoma that attached to the lingual surface of the left mandibular angle and extended from submandibular space to infratemporal space. After the excision of the tumor the patient made a full recovery.