Lancelot, also known as Sir Lancelot and Lancelot du Lac (“Lancelot of the Lake”) is the greatest knight of King Arthur's court and lover of Arthur's wife, Queen Guinevere, best known from Sir Thomas Malory's Le Morte D'Arthur (1469 CE). The character was first developed by the French poet Chretien de Troyes (l. c. 1130-1190 CE) in his Lancelot or the Knight of the Cart (c. 1177 CE) who introduced Lancelot's affair with Guinevere as well as his reputation as a famously skilled warrior.

The character may have originated in Ireland from the fertility god Lug (or Lugh), as perhaps is the case with another of Arthur's knights, Sir Gawain. Gawain's character was established as the greatest knight by Geoffrey of Monmouth in his History of the Kings of Britain (1136 CE) before Chretien elevated Lancelot's role and developed his character. Afterwards, many of Gawain's central attributes (especially his martial skills) were given to Lancelot by later poets following Chretien's model.

In Malory's work, Lancelot's affair with Guinevere finally destroys the unity of Arthur's Round Table of noble knights and allows the villain Mordred to usurp the throne. Mordred's actions lead to the destruction of the kingdom and the deaths of most of the greatest knights while Arthur, mortally wounded, is taken away to the mystical isle of Avalon. The Lancelot-Guinevere love affair is among the most famous in world literature and defines the lovers even as they struggle to resist their passion, rendering them finally heroic figures brought down by the fatal flaw of their relationship.

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Origin Theory:

scholars, however, claim that Lancelot originated in Ireland as a fertility god and was transformed by poets and bards, embellishing on mythological themes, into a noble knight. Scholars Roger Sherman Loomis, Maria Leach, and Jerome Fried claim that Lancelot was originally an Irish solar figure. Leach and Fried note:

The great Irish sun god Lug bore the epithet Lamfada, “Long Hand.” Lug was taken over by the Welsh as Lluch Llauynnauc, Lluch “White Hand.” Lluch, in the Black Book of Carmarthen and Kilwch, has become a warrior of Arthur's, just as the Irish sea god Manannan, in the same texts, is enrolled in Arthur's train as Manawyddan, son of Llyr. Lug turned up in French romance as (at least) two personages. His name was corrupted into Loth; his sobriquet, under the influence of the French name Lancelin, became Lancelot. The accident that lluch as a common noun meant “lake” led to the conversion of the name Lluch into the title “du Lac”, and to Lancelot's acquiring a foster mother, the Lady of the Lake. (602)

Leach and Fried build on the earlier work of Loomis, one of the most highly regarded Arthurian scholars of the 20th century CE, but scholars in the present day largely dismiss this claim as needlessly complicated. Arthurian scholar Norris J. Lacy, for example, claims the simplest explanation for the character's origin is Chretien and the wealth of European legend and medieval folklore he was able to draw from.