The Afanc is the best-known water monster of Welsh legend: a beast in a lake or river pool that causes floods and is finally dragged out by a team of giant oxen. The story is real Welsh folklore, but its most famous version is younger than it looks. The oldest written monster is the addanc of a medieval romance. The tale of the oxen hauling it out of the lake was popularized around 1800 by Iolo Morganwg, a brilliant and notorious forger of Welsh tradition.[1][2] In modern Welsh, afanc simply means “beaver.”[3]
| Other names | Addanc (Middle Welsh romance), avanc |
|---|---|
| Meaning | Modern Welsh afanc = beaver |
| Type | Folklore water monster, not a reported animal |
| Locations named | Llyn Llion; a pool on the River Conwy called Llyn yr Afanc; Llyn y Ffynnon Las in Snowdonia; later writers add Llyn Barfog and others |
| Earliest source | The romance Peredur son of Efrawg (medieval; preserved in 14th-century manuscripts) |
| Key later source | Iolo Morganwg’s “Third Series” of Welsh Triads (published 1801) |
The oldest version: the addanc in Peredur
The earliest monster of this name appears in Peredur son of Efrawg, a medieval Welsh Arthurian romance later included in Lady Charlotte Guest’s Mabinogion translation. In the story, the “Addanc of the Lake” lives in a cave and kills the sons of a king every day, though they are restored to life each night. A maiden warns Peredur that the monster kills by cunning, hiding behind a pillar at the cave mouth and striking with a poisoned dart. She gives him a stone that lets him see the creature without being seen. Peredur runs it through with his lance and cuts off its head.[1]
This addanc is a cave-dwelling killer in a chivalric adventure, not a lake monster that causes floods. It is the only version of the creature that clearly predates the modern era.
The flood, the maiden and the oxen
The story most people know is different. In the version retold in W. Jenkyn Thomas’s Welsh Fairy Book (1907), the afanc lives in Llyn Llion and repeatedly bursts the lake’s banks, flooding the land. No weapon can pierce its hide. A maiden lures it out and lets it sleep with its head in her lap while it is bound in iron chains. When it wakes it attacks her and tries to return to the water. The chains are fixed to the long-horned oxen of Hu Gadarn, which drag the afanc over the mountains to Llyn y Ffynnon Las, a lake in Cwm Dyli below Snowdon. There it can no longer flood anything.[4]
The tale also explains local place names. One ox strained so hard that it lost an eye, giving the names Gwaun Llygad Ych (the Moor of the Ox’s Eye) and Pwll Llygad Ych (the Pool of the Ox’s Eye), along with the pass Bwlch Rhiw’r Ychen where the oxen struggled.[4] A related version places the monster in a deep pool on the River Conwy known as Llyn yr Afanc and has the oxen haul it up the Lledr valley toward Snowdon.[5]
Iolo Morganwg and the triads
Edward Williams, better known by his bardic name Iolo Morganwg (1747–1826), collected and published a great deal of genuine Welsh literature. He also invented a large amount of “ancient” material, including a “Third Series” of Welsh Triads printed in the Myvyrian Archaiology of Wales in 1801. One of these triads names the great horned oxen of Hu the Mighty, which drew the avanc from the lake to the land so that the lake burst no more. Another links the bursting of Llyn Llion to a flood that drowned all of Britain except Dwyfan and Dwyfach.[2][6]
Scholars consider Hu Gadarn’s role as a great culture hero to be largely Iolo’s creation. There is no reliable evidence that most of the afanc-and-oxen story existed as old tradition before him, although it may draw on genuine local folklore about long-horned oxen and lakes.[2] Later collectors repeated Iolo’s version, and it has been part of Welsh folklore ever since.
Why “beaver”?
In Middle Welsh, avanc and afanc could refer to the creature of Llyn Barfog and similar legends. In modern Welsh, afanc is the standard word for the beaver.[3] Beavers lived in Wales into the Middle Ages: in 1188, Gerald of Wales described them building their lodges on the River Teifi, which he said was by then the only river in Wales or England where they could still be found.[7] One common suggestion is that memories of beavers, whose dams flood land and change rivers, fed into stories of a water beast responsible for floods. This is an attractive idea, but it can’t be proven.
Arthur and the afanc of Llyn Barfog
A third tradition gives the job to King Arthur. Llyn Barfog, the “Bearded Lake,” is a small, reedy lake in the hills above Aberdyfi at the southern edge of Snowdonia. Local people there are said to have asked Arthur to rid them of an afanc that killed people and flooded the valley. Arthur rode up on his mare Llamrei, dropped a chain over the sleeping beast’s head, and hauled it out of the water. The mare braced herself against a rock so hard that her hoof left a print in it. That rock, Carn March Arthur (“the stone of Arthur’s horse”), can still be seen on the hillside near the lake. In some tellings Arthur killed the afanc; in others he dragged it to Llyn Cau on Cadair Idris, where it could do less harm.[8]
The hoofprint is a classic piece of landscape folklore: a natural mark in a rock is explained by a heroic event, much like the Ox’s Eye pool in the Snowdon version. The structure of the story is also familiar by now: a flood-causing monster, a binding chain, and an animal strong enough to drag it away. Llyn Barfog has other legends too. The best known is the fairy cow of the Gwragedd Annwn, the otherworldly lake maidens, which made a farmer rich until he tried to slaughter her.[8]
The afanc returns
If the beaver really does lie behind the name, the afanc is now coming home. Beavers died out in Wales in the Middle Ages. In 2021 a small family was released into an enclosure at Montgomeryshire Wildlife Trust’s Cors Dyfi nature reserve, in the same Dyfi valley that Llyn Barfog overlooks. The Welsh Beaver Project, run by the five Wildlife Trusts in Wales, has applied to Natural Resources Wales for a licence for the first official wild release. In March 2026 the Welsh Government recognized the Eurasian beaver as a native species and extended European Protected Species status to beavers in Wales.[9]
The comparison is a little ironic. In folklore the afanc is the creature that floods the land and has to be dragged away. In modern conservation the beaver’s dams are valued for doing something similar on a small scale: holding back water, slowing floods downstream and creating wetlands.[9]
Explaining the Afanc
- A folk explanation for floods. Upland lakes and river pools in Wales can flood dramatically. A monster that bursts a lake’s banks, and is removed to a high, enclosed lake where it can do no harm, explains why one valley floods and another does not.
- Place-name stories. Much of the legend exists to explain names in the landscape, like the Ox’s Eye pool and the Pass of the Oxen.
- Literary invention. The famous version owes a great deal to Iolo Morganwg’s romantic reworking of Welsh antiquity.
- A remembered animal. The beaver, once native and since lost, may lie somewhere behind the name.
For another lake monster with a long literary history, see the Loch Ness Monster, and for a Cornish sea serpent, Morgawr.
References
- “Peredur the Son of Evrawc,” in The Mabinogion, trans. Lady Charlotte Guest (1849). Sacred Texts.
- Mary Jones, “Hu Gadarn,” Jones’ Celtic Encyclopedia, with the text of the Iolo Morganwg triads. maryjones.us.
- Geiriadur Prifysgol Cymru (University of Wales Dictionary), vol. I, p. 41, s.v. “afanc.”
- W. Jenkyn Thomas, “Hu Gadarn,” in The Welsh Fairy Book (London, 1907). Sacred Texts.
- Ben Johnson, “The Legend of the Afanc,” Historic UK.
- Owen Jones, Iolo Morganwg and William Owen Pughe (eds.), The Myvyrian Archaiology of Wales, vol. II (London, 1801), “Third Series” of triads; see also James MacKillop, A Dictionary of Celtic Mythology (Oxford, 1998), s.v. “Dwyfan and Dwyfach.”
- Gerald of Wales, The Journey Through Wales (1191), Book II, ch. 3, on the beavers of the River Teifi.
- zteve t evans, “Welsh Lake Legends and Folklore: Llyn Barfog, the Female Dwellers of Annwn and King Arthur and the Afanc,” Folklore Thursday (20 July 2017), drawing on Wirt Sikes, British Goblins (1880), and W. Jenkyn Thomas, The Welsh Fairy Book (1907).
- “The journey to return beavers to Welsh waterways,” Radnorshire Wildlife Trust (31 August 2026).
Correction note (October 2026): This entry was rewritten from the original sources. An earlier version described the Afanc with scales and glowing eyes and reported a bard who saw it rise from Llyn Tegid by moonlight. None of these details is found in the sources and they have been removed. The illustration above is an artistic impression.