Beli Mawr, son of Manogan, also known as Beli the Great, is a figure appearing in early Welsh genealogies as a legendary ancestor, often situated at the mythical beginnings of several royal pedigrees. Beli’s prominence in genealogy extends back to at least the Old Welsh period, evidenced by references to “Beli Magnus” in the Old Welsh pedigrees found in British Library MS Harley 3859. Additionally, Beli is mentioned in the Old Breton genealogy of St. Gurthiern.
And immediately the emperor set forth with his army. And these men were his guides. Towards the Island of Britain they went over the sea and the deep. And he conquered the Island from Beli the son of Manogan, and his sons, and drove them to the sea, and went forward even unto Arvon.
The Dream of Macsen Wledig
In the tale of Lludd and Llefelys, Beli Mawr, or Beli Uawr, is identified as the father of Lludd Llaw Ereint, Nynniaw, and Caswallon.
Beli the Great, the son of Manogan, had three sons, Lludd, and Caswallawn, and Nynyaw; and according to the story he had a fourth son called Llevelys.
Lludd Llaw Ereint
And the third (army) went with Caswallawn son of Beli, and Gwennwynwyn and Gwanar, sons of Lliaw son of Nwyfre, and Arianrhod daughter of Beli their mother.
The Welsh Triads 35
The second Fortunate Concealment: The Dragons in Dinas Emrys, which Lludd son of Beli concealed;
The Welsh Triads
Caswallon is particularly significant in Welsh legendary history, as he corresponds to the historical figure King Cassivellaunus , who opposed Julius Caesar in 54 BC. The similarity between Beli’s name and that of the British king who faced Caesar, as mentioned in the 9th-century Welsh Latin Historia Brittonum, suggests a connection—Bellinus filius Minocanni.
This form in Historia Brittonum can be traced to an error in Orosius, the 4th-century Latin Christian historian, who referenced Minocynobellinus Britannorum regis filius (son of the king of the Britons), based on Suetonius’s mention of Adminius Cynobellini Britannorum regis filius. However, while this explains the patronym Mynogan/Minocannus, the prevalence of the name Beli in other contexts indicates that not all instances can be attributed to this single scribal error.
In the Welsh versions of Geoffrey of Monmouth’s Historia Regum Britanniae, Beli takes the place of the legendary prehistoric British king known as Hely. Furthermore, the conquerors of Rome, Brennius and Belinus in Geoffrey’s work, are given the Welsh names Brân and Beli. Historical records also attest to Beli as the name of a king or a king’s father in early medieval Wales, Strathclyde, and among the Picts, where the variant Bili is more common. The common Old Breton name and name element, Bili, likely shares origins with Beli.
The name Beli may derive from the Old Celtic name, found in forms like Bolgioj Bolgios and Belgius. This name was borne by the chieftain who led the Gauls’ invasion of Macedonia in 280–279 BC. It’s conceivable that this influential figure Bolgios/Belgios became associated with the powerful British and Gaulish tribal group known as the Belgae, leading to the belief that Beli, stemming from Belgios, was the ancestor of tribal dynasties in Britain.
Please note this is not the same person as Beli Mawr the Celtic God.