What is the name of the giant father of Olwen in Welsh myth?

The giant father of Olwen in Welsh myth is Ysbaddaden, usually called Ysbaddaden Bencawr, or “Ysbaddaden Chief of Giants.” He is the main antagonist of the Welsh tale Culhwch and Olwen.

Culhwch is cursed to marry no one but Olwen, although he has never met her. With help from his cousin Arthur and Arthur’s warriors, he finds Olwen at the remote castle of her father, Ysbaddaden. The giant initially attacks the visitors with a poisoned dart, but the warriors outwit and wound him.

Ysbaddaden agrees to the marriage only if Culhwch completes a series of impossible tasks, known as anoethau. These include hunting the enormous boar Twrch Trwyth and recovering the prisoner Mabon ap Modron. The tasks connect the story to a wider heroic world populated by Arthur and his warriors.

After Culhwch succeeds, Ysbaddaden is stripped, humiliated, and finally beheaded by Goreu, whose brothers the giant had murdered. Custennin is not Olwen’s father; he is her uncle and Ysbaddaden’s abused brother.