Epulis is a benign neoplasms of the oral cavity, derived from the periodontal ligament or connective tissue, occur commonly in dogs and rare in cats. However, it is very rare in horse. The tumor can be very large to interfere with normal mastication. Several forms of epulides can histologically be distinguished in dogs. Fibromatous epulis microscopically characterized by a dense well vascularized stroma populated by expansile mass of stellate fibroblasts surrounded by variable amounts of densely packed fibrillar collagen. The present report is related to a sixteen- years-old mixed breed stallion, had been used for several years in production of snake antivenom. The animal showed abnormality in mastication and difficulties in swallowing food. Therefore, clinical examination was performed. Close examination of the oral cavity revealed that there was a large proliferating mass (measured 15 × 12 cm in diameter) on the gingival of the right mandible. There was no good prognosis, therefore, the animal was euthanized and, subsequently, necropsied. Based on location of the lesion as well as gross and microscopic features, the protruded mass was diagnosed and classified as fibromatous epulis.