Lipoma is a benign tumor of well-differentiated adipocytes that has been reported in some domestic animals. Omental lipomas in human and domestic animals are rare and reported as a case report. This study aimed to report an omental lipoma in a slaughtered sheep. In the observational examination of a sheep in a slaughterhouse in Tehran Province, Iran, and during the inspection of the abdominal area, a mass was seen on the greater omentum. The mass was sampled and placed in 10% formalin for histopathology. The mass was single, soft, dense, capsuled, oval, weighing 150 g, and 4.5×3.5 cm in size. Microscopic examination showed omental mass composed of uniform and mature lipocytes encased within a thick layer of immature connective tissue. The final diagnosis was primary benign lipoma. Lipoma can occur anywhere in the body where there are fat cells, and probably obesity and trauma are important risk factors for its occurrence. The size of the lipoma mass may help predict the age of the mass.