Early sources include Nennius's chronicle the History of the Britons from the 9th century, and Welsh tales such as the four branches of the Mabinogi and Culhwch and Olwen, which perhaps originate in the 11th century. None of these feature Arthur in a prominent role.
The stories were developed into more familiar forms in the 12th century. The Welsh cleric Geoffrey of Monmouth's Latin chronicle The History of the Kings of Britain told of Arthur, Merlin, Mordred, and Guinevere. Chrétien de Troyes, writing in Old French, introduced several of Arthur's knights such as Lancelot and Percival. Other notable contributors include Thomas of Britain, Wolfram von Eschenbach and Marie de France, as well as many anonymous authors. Thomas Malory, who wrote in the 15th century, supposedly while in prison, collected the stories into the popular Le Morte d'Arthur and also introduced several new characters. Another important retelling was Alfred Tennyson's Idylls of the King in 1859.
Because the stories where written by many authors over several centuries there is no official version, and the different tales often do not agree.
List of Arthurian Cycle names and meanings
List of Arthurian Characters