fl. 475-537 CE
Legendary king of Britain; one of the last kings of the Britons of the whole isle according to Geoffrey of Monmouth.
The Common Legend
Arthur was born of a liason between Uther Pendragon and Igraine wife of Gorlois, duke of Cornwall, situated at Tintagel. The magician Merlin disguised Uther with a potion, transforming Uther and his companions into the form of Gorlois and his companions, while Gorlois himself was slain in battle. Upon hearing of the duke's death, Uther married Igraine, and Arthur was born legitimately. Merlin then takes Arthur and has him raised away from the dangers of the court, leaving the child as a foundling with Sir Ector. Ector raises Arthur as his own, until the boy reaches squirehood, when he pulls the magical sword from the stone, proving his rightful place as the new king of Britain.
Arthur's early reign is marked with rebellions, with many rulers seeing him as a childish no-one easily defied. Arthur dominates them in battle, however, and succeeds in uniting most of Britain behind him, the exception being his brother-in-law Lot of Lothain. Lot is married to Arthur's sister (the identity shifts, but is usually Morgause), and father to his nephews Gawain, Agravain, Gareth, and Gaheris. Arthur meanwhile is lured under a spell to sleep with Morgause and beget Mordred upon her.
During this time, Arthur loses his sword, and is directed by Merlin to the Lady of the Lake, who gives him Excalibur. He also marries Guenevere, who brings with her the famous Round Table.
After subduing Britain, Arthur turns towards the continent, and proceeds to attack Rome (the reasons are varied). After winning, he returns to Britain, where he takes a backseat to the adventures of his knights: Gawain and Gareth, sons of his sister Morgause; Ywain, son of his sister Morgan; Perceval, Tristain, and most famously Lancelot, who begins an affair with Guenevere. The climax of these adventures is the quest for the Holy Grail, which decimates the Round Table, and puts an end to the enchantments of the realm.
Guenevere is accused of adultery but aquitted though combat. She is then abducted by Melegant of Gorre, and Lancelot is charged with rescuing her. The adultery charge is made again, this time by the sons of Lot, who convince Arthur to arrest Lancelot. Lancelot escapes, while Guenevere is set to burn at the stake. Lancelot rescues Guenevere, and escape together. After combat, Lancelot returns Guenevere to Arthur, and escapes to France. Arthur goes to pursue Lancelot, leaving Mordred as regent; Mordred usurps the throne, and attempts to force Guenevere to marry him. Arthur returns to Britain, where he goes to war with Mordred. They slay each other at the Battle of Camlann, and Arthur is borne away to the isle of Avalon, while his seneschal Bedevere returns Excalibur to the Lady of the Lake.
The legend says then that Arthur did not in fact die, but has lain sleeping on the isle of Avalon, awaiting the time to return to Britain during its greatest need.
Arthur as History
Leaving aside the disputed "Arthur stone" and "Arthur cross", the earliest references to Athur are Welsh and Latin:
Gochore brein du ar uur
Caer cein bei ef arthur
He [Gwawrddur] brought black crows to a fort's
Wall, though he was not Arthur.
It celebrates Arthur's prowess as a warrior; if Kenneth Jackson, Ifor Williams, John Koch and other scholars are right and the B text is archaic, then this reference to Arthur is not only the oldest reference, but clearly shows that he was known as "Arthur" by the late sixth/early seventh century, and not by Artorius or Arthrwys.
However, some scholars date the poem, or at least the current form, to the ninth century and based on an oral version.
The history is a fantastic one, full of gods turned into kings, miracles, and portions of actual history mixed together into a confusing mess. If we were to only rely on HB for historical attestations to Arthur, we would be highly mistaken, since it is full of fictional figures such national founders as Brutus and Hengist and Horsa. Since these are obviously mythological figures, how do we know Arthur isn't?
Lack of References
He does mention a few other figures known from Welsh sources, in particular Maelgwn Gwynedd, whom he famously condemns as a murderer and "sodomite". Of the five kings he mentions, they are all contemporaneous with Gildas; if Arthur was earlier, he'd have no reason to mention him, whether he was a hero or not. On the other hand, there is some debate as to whether the king Cuneglasus is Arthur, based on a few details included in Gildas' description of him, as mentioned below; most important, he calles Cuneglasus a bear--which could easily be a pun on "Arthur", if "Arthur" is a nom de guerre.
Possible Historical Figures
If Arthur is not the figure known from romance and pseudohistory, could he have his origins in one or more historical figures? Could one of them be the real Arthur, and "Arthur" a nickname? It's possible; and there are several candidates for the historical Arthur:
His name certainly is close to "Arthur"--it is a gens meaning "plowman", and native to Campania (southern Italy). However, the names may only be suggestive coincidence, with Arthur coming from the star name Arcturus--the "bear watcher", refering to the constellation Boötes--the plowman. Arth in Welsh means "bear", and so there may be no actual relationship between Arthur and Artorius except as a coincidence. Or, Arthur may have held that name as a way to recall Artorius.
Some of Arthur's military campaigns mentioned by Nennius may have been inspired by Castus' campaigns against the Caledonians, transfering them to the later Saxons.
What makes Riothamus interesting is that his name may be a title--*ri[g]o-tamos "highest king" or "highest leader". The possibility that it is a title means his true name is unknown. His time is near that of Arthur, though early; his crossing into Gaul may, along with the crossing of Artorius, have influenced the story of Arthur's crossing into Gaul to take on Rome. However, if so, the details are obviously reversed, and instead of defending Rome like Artorius and Riothamus, Arthur defeats Rome.
Geoffrey Ashe says that his last known place in Burgundy was near the town of Aballo--modern Avallon, France (95). The connection between Aballo and Avalon, if true, is unmistakable.
Arthur as Myth & Legend
With the introduction of the Normans to England, Arthur became a figure of romance and a useful tool of propaganda, for Arthur, like the Normans, was an enemy of the Saxons. Arthur and his court as a subject for romance was introduced by the Bretons, whose minstrels were popular at the courts of France and its neighbors.
The most famous and arguably greatest romancer was Chretien de Troyes, a Frenchman attached to both the Countess of Champagne and the Duke of Flanders, both of whom were close kin of the Plantagenet kings of England. In Chretien, Arthur presides over a court of adventure; Lancelot and Perceval first take shape here, inspiring future writers. More importantly, Arthur himself takes a backseat to the adventures of his knights, unlike in Welsh legend where he was usually an important player. Similar in effect was Marie de France, whose lais, inspired by Breton lais, also put Arthur in the background, overseeing a fairytale court.
The second important writer, a contemporary of Chretien and Marie, was Robert de Boron, a Burgundian knight who first combined the story of Arthur and the Grail with Avalon, and with that of Joseph of Arimathea and the Last Supper, making it an explicitly Christian story. De Boron's "Merlin" follows Geoffrey closely in detailing the conception of Arthur; he also introduces the Round Table and the Sword in the Stone.
The so-called "Vulgate" version--a five romance epic--finalized the various French and Latin versions of Arthur's story, combining elements of Geoffrey, Chretien, and de Boron, while introducing new characters such as Galahad, the pure knight who wins the Grail. It may have been the work of Cicstercian monks, which would account for the invention of Galahad.
For a fuller treatment, see Arthurian Mythology.
Arthur and Other Saviors
One of the distinctive features of Arthur's character is that he is prophecied to come back from Avalon and restore Britain to the Britons; this sort of messianic hope is not unusual for an oppressed people to indulge in, and the Welsh were no different. Arthur, however, is not the only messianic figure in Welsh literature; the "Armes Prydein" in the Llyfr Taliesin prophecies that Cadwalladr will return with his armies to drive out the Saxons. It also names a Cynan as coming with Cadwalladr; whether this Cynan is meant to be Conan Meriadoc, the mythical founder of Brittany, is not known.
Did Arthur Exist?
Ultimately we have no concrete evidence for Arthur's existence: no artifacts, no contemporary accounts mentioning an "Arthur", nothing written until Nennius' history written at least three hundred years after Arthur's believed time.