Retrobulbar hydatid cysts are extremely rare while non-orbital forms constitute a still frequently encountered disease in underdeveloped countries. This report concerns a patient with a primary hydatid cyst in the orbit. A 22-year-old female patient was admitted to our hospital with proptosis of her right eye, conjunctival edema, hyperemia and headache. The family and patient's own past history were significant for continuous contact with sheep. The neurological examination revealed a retrobulbar mass and limited ocular motility in lateral direction on the right side. The papilledema was found in ophthalmoscopic examination and loss of vision was fixed. The eyeball was non-reductible and non-pulsatile. A frontoparietal craniotomy and orbitotomy was performed and then the mass was removed totally. This case was accepted as a primary infection because of no findings and previous history of liver or lung cysts. In the treatment of orbital hydatid cysts; early diagnosis, surgical excision and then systemic use of albendazole are suggested. Although cyst rupture is rather common, it sometimes results in severe anaphylactic reaction anaphylaxis, incomplete removal or secondary implantation. To avoid of a cyst rupture, intraoperative aspiration is recommended.