An unusually large complex odontoma of the maxilla, occupying the entire maxillary sinus with expansion into the floor of the orbit and left nasal fossa, is reported. Although occurrences of complex odontomas are not considered rare, odontomas attaining extremely large sizes, especially involving the entire maxillary sinus with extension to the orbital floor and nasal fossae, are indeed, rare. In this article, the literature is reviewed to identify the common clinical, radiographic, and histologic characteristics of such lesions, and the outcome of treatment is discussed. Complex odontomas occasionally have significant growth potential, especially in the first two decades of life. Early recognition and consideration for surgical excision are key to successful management of this common odontogenic lesion. When odontomas extend beyond the alveolar process into the fascial planes, nasal fossae, paranasal sinuses, and orbits, computed tomography can readily demonstrate the extent and boundaries of the lesion.