Ambrosius Aurelianus

Emrys Wledig. A crude illustration from a 15th-century Welsh language version of Geoffrey of Monmouth’s Historia Regum Britanniae

Ambrosius Aurelianus (Welsh: Emrys Wledig; Anglicised as Ambrose Aurelian and called Aurelius Ambrosius in the Historia Regum Britanniae and elsewhere) was a war leader of the Romano-British who won an important battle against the Anglo-Saxons in the 5th century, according to Gildas. He also appeared independently in the legends of the Britons, beginning with the 9th-century Historia Brittonum. Eventually he was transformed into the uncle of King Arthur, the brother of Arthur's father Uther Pendragon, as a ruler who precedes and predeceases them both. He also appears as a young prophet who meets the tyrant Vortigern; in this guise, he was later transformed into the wizard Merlin.