Introduction: - Ovarian sex cord-stromal tumours are rare, comprising only 8% percent of all primary ovarian tumours. Ovarian fibroma is the most common benign pure stromal tumour. It has no specific clinical manifestation, most of which are pelvic or adnexal masses. Case report: - This is 59 years old woman came to Orotta National Referral Maternity Hospital On 02-2-2023 with complaint of abdominal distension and pain of one-year duration. The distention progressed slowly and she lost weight profoundly which she can’t quantified despite having good appetite. Her menses stopped 15 years back, then-after she denies any history of vaginal bleeding or discharge. She had no any alteration in bowel habit but she experiences occasional shortness of breath especially when she sleeps without pillow. she was chronically sick looking, in mild distress with respiratory rate 20 breaths/minute with chest was clear to auscultation with decreased air entry on right lower lung field. Abdomen was grossly distended, shiny without visible collateral vein. On palpation, she had huge abdominopelvic mass of about 36 cm by 20 cm, hard, mobile, with rough surface and irregular border. Her haemoglobin was 12.82g/dl and platelet of 504.7x103/µL. Trans-abdominal ultrasonography showed huge solid pelvic mass with ascites and hydrothorax. The serum level of cancer antigen 125 (CA125) was 91.28 U/mL, the carcinoembryonic antigen (CEA) was 34.87 ng/mL and alpha-fetoprotein (AFP) and CA19-9 were within normal range. At laparotomy, there was ascites and a huge globular mass measuring 30 cm was observed on the left ovary. The right ovary, uterus, omentum, and pelvic lymph node were unremarkable macroscopically. Postoperative recovery was uneventful and histopathologic result revealed left Ovarian Fibrothecoma with benign endometrial polyp. Conclusion:- Ovarian fibrothecoma should be considered in women with pelvic pain and a large pelvic mass. In women with ascites and mildly elevated CA 125, the ovaries should be thoroughly investigated as they can be normal initially in imaging studies and gynaecological assessment. Radical surgical excision is the preferred treatment for postmenopausal women and is associated with a good prognosis.