Ranulas are cystic lesions in the floor of the mouth. They are either retention cysts of the excretory duct of the sublingual gland or pseudocysts formed by excretory duct rupture followed by extravasation and accumulation of mucus in the surrounding tissue. We report the case of a premature newborn with a congenital ranula in the floor of mouth. The ranula caused no discomfort or complications, so that immediate intervention was not necessary. The cyst resolved completely by the age of 4 months. Complications in newborns especially include airway obstruction and feeding difficulties. Surgical treatment options are needle aspiration, excision of the ranula, marsupialization, cryosurgery, and--in addition to excision of the cyst--removal of the ipsilateral sublingual gland. Sclerotherapy has shown good results as well. As many congenital cysts resolve or rupture spontaneously, they should be observed for potential resolution for several months in uncomplicated cases.