Human hydatid cyst is a wide spread disease. It is an endemic disease in Iran. Hydatid cyst is extremely rare in the female reproductive organs. This is a case report of ovarian hydatid cyst in a 42-year-old woman. She presented with feeling of enlargement of abdomen and abdominal pain. On physical examination, a large mass in lower abdomen palpated. Ultrasonography reported a heterogeneous multicystic mass measuring 155×97 mm in hypo gastric area. The CT-scan with IV contrast reported a huge cystic lesion, containing multiple septi that could be due to ovarian lesion. After surgery, histopathological examination showed typical laminated &germinative layers with hexagonal scolecies of hydatid cyst. Since the common sites of hydatid cyst are liver, lung, etc and the imaging studies are highly diagnostic for hydatid cysts; this illustrated case is interesting for uncommon site, not suggested by imaging studies and with clinical (surgical) impression of malignant ovarian tumor.