NIGHTBRINGER | The Arthurian Encyclopedia

Osla Gyllellvawr

‘Osla Big-Knife’, ‘Osla Great-Knife’

One of Arthur’s warriors in Welsh legend. He carried a knife called Bronllafyn Short Broad, which was so big that it could be used as a bridge for armies to cross bodies of water.

Osla accompanied Arthur on the epic hunt for Twrch Trwyth. At the Severn River, Osla lost his dagger from the sheath while running after the boar; the sheath filled with water and pulled Osla to the bottom of the river.

He features in the Mabinogion story of the The Dream of Rhonabwy, oddly, as a Saxon adversary of Arthur at Badon. He is perhaps, then, to be identified with Octa, the son or grandson of the Saxon Hengist.

Evans and Bromwich suggests that there’s a confusion between the names Osla and Offa, where the latter is a Mercian king in the eighth century, between 757 and July 796, when he died. He built Offa’s Dyke (Welsh: Clawdd Offa) on the border of Wales and England. Genealogical references to Offa Kyllellvawr urenhin Lloegr (Offa Great-Knife, king of England) support the theory.

Culhwch and Olwen | Late 11th century
Breudwyt Rhonabwy | 13th century