In Irish mythology, Deichtine was the sister of Conchobar mac Nessa and the mother of Cú Chulainn. Her husband was Sualtam, but Cú Chulainn's real father was Lugh of the Tuatha Dé Danann. Deichtine's mother was Maga, daughter of Oengus Og, and her father was Cathbad the Druid. Her sisters were Finchoem, mother of Conall the Victorius, and the mother of Naiose and his brothers. Although Conall the Victorious was a bitter enemy of Anluan and Cet mac Maga, they were his maternal uncles. Cet even protected the pregnant Finchoem until she gave birth and it was prophesized that Conall would be his slayer.
Deichtine was Conchobar's charioteer. When a flock of birds descended on Emain Macha and ate all the grass, the Ulstermen decided to hunt them. They set off after them in their chariots and chased them until night fell. It began to snow, so they decided to seek shelter. They found a house and were welcomed in by the young man who lived there. His wife was in labour at the time, but he showed them hospitality and served them food and drink.That evening his wife gave birth to a baby boy, and at the same time a horse outside the house gave birth to two colts. The Ulstermen went to sleep, but when they woke up they found themselves at the Brug na Bóinne "Newgrange". The house, the man and his wife had vanished, but the baby and the two colts remained. Deichtine took the boy as her foster son and they returned to Emain.
Soon after the boy fell ill and died. Deichtine took a drink, and a tiny creature leaped from the cup into her mouth. When she fell asleep, Lug appeared to her and told her it was his house they had stayed in that night, and that his child was in her womb. She married Sualtam and gave birth to a son.