Background: Hydatid disease is a zoonotic condition caused by the adult or the larval form of Echinococcus granulosus or less commonly Echinococcus multilocularis. The clinical presentation depends on the site of involvement. Many cases are not symptomatic and may be discovered accidentally. Hydatid cyst of the ovary is an extremely rare presentation that accounts for 0.2–1% of the diagnosed cases. It may be mistaken for ovarian cysts or cystic tumors of the ovary. The diagnosis is often based on the couple ultrasound-hydatid serology, but only the histopathological study can confirm the diagnosis of ovary hydatid cyst. Case report: A 40-years-old woman (G4P4), consulting for lower abdominal pain and frequent urination for the last 3 months. The clinical examination was normal besides a discrete pain in the supra-pubic region. Ultrasound of the abdomen showed evidence of cystic mass on the left ovary. A computerized tomography scan of the abdomen revealed the same lesion with no enhancement after contrast injection. In laparotomy we found a latero-uterine cystic lesion measuring approximately 6,5x3,5x4,7 cm there was evidence of a hydatid cyst of the left ovary. The treatment consisted on aspiration with injection of chlorhexidine. The patient underwent a hysterectomy with salpingo-oophorectomy with simple postoperative course. The diagnosis of hydatid cyst was confirmed through histopathological examination. Conclusion: The diagnosis of hydatic ovarian cyst is often based on the couple ultrasound-hydatid serology, but only the histopathological study can confirm the diagnosis The surgical treatment depends on the volume and location of the cysts. Hysterectomy remains the treatment of choice to avoid recurrences. Medical treatment is only necessary when the excision is incomplete or for multiple locations.