Conan Meriadoc (; ; ) is a legendary Celtic leader credited with founding Brittany. Versions of his story circulated in both Brittany and Great Britain from at least the early 12th century, and supplanted earlier legends of Brittany's foundation. His story is known in two major versions, which appear in the Welsh text known as The Dream of Macsen Wledig, and in Geoffrey of Monmouth's Historia Regum Britanniae. Both texts associate him with Magnus Maximus (Macsen Wledic, reigned 383–388), a Roman usurper against the Valentinianic dynasty who was widely regarded as having deprived Britain of its defences when he took its legions to claim the imperial throne. Conan's cousin or sister, Saint Elen, is said to have been Macsen Wledic's wife. Early evidence The earliest undisputed evidence connecting Conan to the foundation of Brittany appears in the Life of Saint Gurthiern, included in the Kemperle Cartulary compiled between 1118 and 1127. This text traces the descent of Gurthiern back to the ancestor figure Beli Mawr, given as a son of Outham Senis (Outham the Old), the figure known in later sources as Eudaf Hen and Octavius. Outham is given another son, Kenan (an Old Welsh spelling of Conan), who is said to have been the founder of Brittany. This reference shows that the Conan story was known in Brittany from a comparatively early date, but certain evidence suggests that it was imported from Wales. The text's compiler, Gurheden, says that his source for the information was one "Iuthael son of Aidan"; while the name Iuthael is a Brittonic name known in Wales and Brittany as well as Devon and Cornwall, the Gaelic Aidan is not attested in early Brittany but is known in Wales. Additionally, Gurthiern's genealogy corresponds strongly with the descent elsewhere attributed to the Welsh saint Cadoc, further suggesting a Welsh origin. Conan Meriadoc also appears in the prologue to the Latin Life of Saint Goeznovius, though the date of this text is disputed. The prologue, the only part of the work still extant, survives in a copy by the French historian Pierre Le Baud (died 1505), but contains a passage claiming it was originally written in 1019 by a certain Guillaume, a servant of Bishop Eudo. This date has been defended by Gwenaël Leduc and Léon Fleuriot. However, Hubert Guillotel has argued that the text dates instead to the mid-12th century. There is evidence that Conan Meriadoc