AbstractGiant ovarian cysts are categorized with sizes >10 cm. After reaching huge diameters, these rare tumors cause clinical symptoms such as nausea, vomiting or abdominal pain. We present a 29-year-old woman with a giant unique cystadenoma represented with unusual clinical features like low back pain and progressive constipation. Specific imaging methods demonstrated an adnexal lesion in the form of an enormous ovarian cyst; afterward, an open laparotomy was recommended to access the abdominal cavity. The critical role of timely diagnosis and accurate workups for giant ovarian cysts in increasing patients’ life expectancy and quality of life is discussed.