Sir Lancelot was a character in the legend of King Arthur, and was a Knight of the Round Table. Sir Lancelot of the Lake was one of the most trusted knights of King Arthur's Round Table, but this soon changed when he fell in love with the king's wife, Queen Guinevere. He was raised by the Lady of the Lake, hence his title Lancelot Du Lac. Sir Lancelot was the only knight known to defeat King Arthur during a jousting match. He is also known briefly as the father of Sir Galahad, the greatest knight of all Camelot. Sir Galahad's mother is also possiblly Elaine Of Corbenic. Lancelot's affair with Elaine later caused him and Guinevere to part ways.
Lancelot was a Red Cross Knight, which meant that he was one of the knights who was in the quest to find the Holy Grail. He saw the ascension of Sir Galahad. His first appearance as a main character is in Chrétien de Troyes' Le Chevalier de la Charette ("The Knight of the Cart"), written in the 12th century, where his exploits are recounted in the section known as the Prose Lancelot, often with conflicting background stories and chains of events.
Lancelot is a cheater, he took Arthur's wife Guinevere. He is also said to be handsome, and very comfortable with a sword.