Ravana is the demon king the epic Ramayana. His birth was not divine or through magical means. So who is the mother of Ravana? As per epic Ramayana, Ravan was the son of Kaikasi (Kaikashi).
Kaikasi was the daughter of Sumali, a rakshasa chieftain. She married Sage Vishravas to have powerful children who will help the rakshasas in overcoming the devas, or demi gods.