Old Welsh: Guortepir
Middle Welsh: Gwrdeber, Gwerthefyr
Uortiporius, Vortipor, Vortiporius, Vortiporous
The third King of Britain after Arthur, according to Geoffrey of Monmouth. He wrote a chapter titled:
Uortiporius, being declared king, conquers the Saxons
Vortipore succeeded to the throne after the previous wicked king, Conan, fell off a horse and broke his neck. Vortipore successfully battled off a wave of Saxon invaders and reigned for seven years. Vortipore is a historical figure, though the position attributed to him by Geoffrey is invented.
Gildas mentions him as a tyrannical king of Dyfed (Demetia), which he apparently inherited from his father, Agricola. Vortipore had a great-grandson named Arthur of Dyfed.
Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
De Excidio et Conquestu Britanniae | Gildas, c. 540