Owain mab Urien

Owain mab Urien (or Owein) (died c. 595) was the son of Urien, king of Rheged c. 590, and fought with his father against the Angles of Bernicia. The historical figure of Owain became incorporated into the Arthurian cycle of legends where he is also known as Ywain, Yvain, Ewain or Uwain. In his legendary guise he is the main character in Chrétien de Troyes's Yvain, the Knight of the Lion and the Welsh Romance Owain, or the Lady of the Fountain, which corresponds to Chrétien's poem.

Our chief references to the historical Owain appear in the poems of Taliesin, Urien's bard. In one poem, he appears as the victor of the Battle of Alclud Ford. Another, Gweith Argoed Llwyfain ("The Battle of Argoed Llwyfain"), tells of Owain's part in a battle between the men of Rheged under Urien and the men of Bernicia under "Fflamddwyn" (Firestealer), possibly the Anglian king Theodric. When Fflamddwyn demands hostages, Owain shouts defiance and inspires the men of Rheged to fight rather than give tribute to the English.

Taliesin also composed Marwnad Owain, an elegy to Owain. In the poem, it is said that Owain slew Fflamddwyn:

He inherited the kingdom of Rheged when his father was killed, but was immediately beset by his British neighbours, Gwallawc Marchawc Trin of Elmet and Dunaut Bwr; the former attacking Owein's brother Elffin whilst Owein and Pasgen, another brother, fought Dunaut.

...
Wikipedia