Welsh name for the 11th-century Arthurian narrative known in English as Culhwch and Olwen, also Kilhwch, Kulhwch and Olwen. Culhwch is one of the most important texts for the study of the Arthurian cycle because of its antiquity, its kinship with early Irish narrative, the roll-call of heroes associated with Arthur, and its foreshadowing of themes which recur in later non-Celtic narratives. Whatever Culhwch's interest as a story, it has attracted continuing attention because it is ‘purely Celtic’, i.e. lacking embellishments from Continental literature. Its main plot is known to folklorists as The Giant's Daughter, of which the most familiar in classical tradition is the story of Jason and Medea (Folk motifs: G530.2; E765.4.I.I.; H335). Although orthographical evidence suggests that the original narrative may have been composed before 1100, the only complete text is found in the Red Book of Hergest (c.1400); an incomplete text is found in the White Book of Rhydderch (c.1350–95).
The story begins when Cilydd, son of Celyddon Wledig [W gwledig, ruler, prince] seeks to marry a woman as well-born as himself. He chooses Goleuddydd, daughter of Anlawdd Wledig. Pregnant soon after the wedding night, Goleuddydd becomes deranged and wanders through wild country, giving birth to her noble son in a pig-run and shortly afterwards dying. To find a new wife for himself, Cilydd kills the king of Doged and carries home his wife. In her unhappiness the step-mother curses Culhwch, prophesying that he will not touch woman until he has won Olwen, daughter of Ysbaddaden, a crafty and powerful giant. Cilydd tells his son this task will be easy to accomplish if the boy will only seek help of King Arthur, a cousin; on meeting Arthur he should ask to have his hair trimmed. Hearing this, Culhwch, who has fallen in love with Olwen without having seen her, sets out for Arthur's court. Culhwch's arrival is evocative of Lug Lámfhota's arrival at Nuadu's court in Cath Maige Tuired [The (Second) Battle of Mag Tuired]. At first he is refused by Arthur's porter Glewlwyd Gafaelfawr, but he persists until the king demands Culhwch be admitted. Culhwch asks that his hair be trimmed and recites a lengthy roll-call of Arthurian heroes including the children of Dôn. So winning is Culhwch that Arthur agrees to help him in winning Olwen, and they are joined by Cei, Bedwyr, Cynddelig Cyfawydd, a guide, Gwrhyr Gwalstad leithoedd, an interpreter, and Menw, an illusionist.
After a long journey Culhwch and Arthur meet the herdsman Custennin, whose confidence is won with a gold ring; his wife proves to be the sister of Goleuddydd, Culhwch's mother. Both Custennin and his wife are concerned at reports that no one leaves Ysbaddaden's castle alive. None the less Culhwch, Arthur, and the company go on to the nearby castle, where Culhwch meets Olwen, whose name means ‘flower track’ because four white clovers spring up wherever she steps. Olwen accepts Culhwch's profession of love but says that she can not join him until he asks the permission of her father, Ysbaddaden. The giant is not receptive to guests. He throws three poisoned stone spears at Culhwch and Arthur's party, each one of which is turned back against the thrower. Thus wounded, Ysbaddaden hears Culhwch's entreaty. The father agrees to give his daughter's hand to Culhwch if he can accomplish forty apparently impossible tasks. Some are frivolous, such as finding honey nine times sweeter than that of the first swarm out of the hive. The first group of tasks require eight primary agricultural labours, such as ploughing waste land so that food might be grown, and five secondary labours to complete the ploughing. A second group of tasks pertain to the collaring and chaining of the great boar Twrch Trwyth while enlisting the help of several foreign heroes. The boar must be made to yield his razor, scissors and comb. Culhwch agrees to each task rather insouciantly, and accomplishes thirteen of the original plus three not previously mentioned. The recitation of the tasks makes tedious reading, but handled by an exceptional storyteller they may have been engaging to early audiences. The hunting of Twrch Trwyth includes several place-name stories. Culhwch pursues the boar from Ireland to Wales, from Wales to Brittany, and from there to Cornwall. He seizes the razor and scissors at the mouth of the Severn, while Arthur's men capture the comb in Cornwall. These help the giant Ysbaddaden prepare for his daughter's marriage. At the end of the narrative Culhwch wins Olwen and spends the night with her.