Many scholars trace the first mention of Arthur to a Welsh poem called the "Gododdin," which elegizes Scottish warriors. The "Gododdin" has been attributed to a sixth-century poet named Aneirin and is often considered Britain's earliest surviving poem. Arthur is named in just one line. Other possible references to Arthur from this time period are in the "Historia Britonum" (History of Briton), written around AD 800, and in the "Annales Cambriae" (Annals of Wales), probably written a few hundred years later. Both of these texts were used as sources for multiple histories of Britain and Wales, and both are likely compilations and revisions of earlier texts. In addition, their true authors are in question, and their accuracy can't be proven.
The beginnings of King Arthur as we recognize him can be traced to Geoffrey of Monmouth. This priest and author wrote the "Historia Regum Britannae" (History of British Kings) in the early 1100s. Scholars believe that Geoffrey based this text in part on the "Historia Britonum" as well as earlier histories. Some of his contemporaries went so far as to accuse him of fabricating much of his writings.
However, the "Historia Regum Britannae" became incredibly popular and spread throughout Europe. It influenced French writers and led to the creation of the Arthurian romance. The poet Chretien de Troyes wrote several poems about love and chivalry in the mid-1100s that incorporated tales of Knights of the Round Table. The most significant ones established the romance between Lancelot and Guinevere and told the story of the search for the Holy Grail.
The Vulgate Cycle, or Prose Lancelot, comprises prose stories that expand on de Troyes' themes and tie Christianity even more into the Arthurian legend. Not clearly attributed to an author, these stories were written between 1210 and 1230. They explain how Joseph of Arimathea, a Biblical figure who donated his tomb to Jesus after the crucifixion, brought the Grail to Britain. In a later story, Galahad, the illegitimate son of Sir Lancelot, was able to discover the Grail because he was so pure and devoted. The Vulgate Cycle was followed by the post-Vulgate a few years later, which revised and added material to the existing stories. This is the source for the Lady in the Lake myth and the tale of Mordred as Arthur's son by his sister.
Sir Thomas Malory's compilation "Le Morte d'Arthur" (The Death of Arthur) is probably the best-known version of the Arthurian legends. It was first printed in 1485 and contains the entire story of King Arthur's life, as well as the quest for the Holy Grail and stories about two different Knights of the Round Table: Sir Gareth and Sir Tristan. Up until this time, most of the retellings focused more on pagan and Celtic elements. But in Malory's version, Christianity plays a large part. For example, Guinevere becomes a nun and Lancelot becomes a monk after their affair is discovered.
Malory's version became the basis for many more retellings. This includes the "Idylls of the King" by Victorian poet Lord Alfred Tennyson, and the T.H. White novel "The Once and Future King," which led to the Disney film "The Sword in the Stone."
With such a long and varied history, it seems impossible that Arthur could have been a real person, or that Avalon could have been a real place. But some still believe. We'll look at the theories in the next section.