What is the name of the magical boar hunted by King Arthur in Welsh myth?

The magical boar hunted by King Arthur in Welsh myth is Twrch Trwyth.

His elaborate pursuit appears in the Welsh prose romance Culhwch and Olwen, probably composed around the year 1100. Arthur and his companions must chase the boar to obtain a razor, scissors, and comb needed to groom the giant Ysbaddaden. The objects are carried between Twrch Trwyth’s ears, making the hunt more than a simple royal expedition.

The boar and his seven offspring are driven from Ireland across Wales and toward Cornwall. Arthur’s hound Cafall and other hunters take part, while the chase involves river crossings, magical transformations, and deadly resistance from the animals. Eventually, the boar is forced into the sea off Cornwall.

A common mix-up is Ysgithyrwyn, another dangerous boar in the same tale. Ysgithyrwyn is the “Chief of Boars,” whose tusk is also required for Ysbaddaden’s grooming. He is not the principal quarry named in this question. Twrch Trwyth also has earlier Arthurian associations, including a ninth-century reference to Arthur pursuing a boar with his dog Cavall.