Fetal ovarian cyst is diagnosed at the rate of one per 2,500 live births and its behaviour in utero may range from spontaneous resolution with no further consequences to torsion, necrosis, and to the necessity of surgical treatment in the postnatal stage. Ovarian cyst torsion in a fetus results in the loss of its reproductive function in adult life. The authors present a case of spontaneous resolving fetal ovarian cyst. The lesion was diagnosed during an ultrasound scan in 30^th week of pregnancy. An ultrasound scan performed two weeks later revealed symptoms of cyst torsion; the lesion was 5.7 cm in diameter, heterogeneous, and had a normoechogenic inside. A subsequent ultrasound exam showed a lesion with a diameter of 2.16 cm. An ultrasound exam of the newborn's abdominal cavity performed on the second day showed that the cyst was six mm in diameter. However, the cyst did not show on an ultrasound scan made on the fourth day.