A case of a 53-year-old postmenopausal woman presenting a giant ovarian cystic mucinous tumor weighing 24 kg is reported here. When she was seen first at our outpatient clinic, she had gross abdominal distension since 2 years, and she complained of unbearable aggressive pain. Her computed tomography (CT) scan was done which came suggestive of ovarian serous cystadenoma of large massive size 35 x 40 x 32 cm with moderate ascites. On exploratory laparotomy, a giant, totally cystic, vascularized and smooth mass attached to the right ovary was encountered. On the postoperative tenth day, she was discharged without any problem. Histopathology report of the right ovarian cystic mass came suggestive of multiloculated cyst with capsule intact with Borderline Mucinous tumor of right ovary weighing 24 kg. This is both one of the largest known examples in the literature and the largest ovarian cyst ever seen at our institution.