Trahaearn ap Caradog (died 1081) was a king of Gwynedd.
On the death of Bleddyn ap Cynfyn in 1075, it appears that none of his sons were old enough to claim the throne, and Bleddyn's cousin Trahaearn ap Caradog, seized power. The family is thought to have originated in Arwystli, on the border between Gwynedd and Powys. The same year Gruffydd ap Cynan landed on Anglesey with an Irish force, and with the assistance of the Norman Robert of Rhuddlan defeated Trahaearn and gained control of Gwynedd. However tension between Gruffydd's Irish bodyguard and the local Welsh led to a rebellion in Llyn and Trahaearn took the opportunity to counter attack, defeating Gruffydd at the battle of Bron yr Erw, also in 1075, and forcing him to flee back to Ireland.
In 1078 Trahaearn was campaigning in South Wales, defeating Rhys ab Owain of Deheubarth, who had been responsible for the killing of Bleddyn ap Cynfyn, in a battle at Gwdig. Rhys was forced to flee, and later the same year was killed by Caradog ap Gruffydd of Gwent. This was hailed in the annals Brut y Tywysogion as "vengeance for the blood of Bleddyn ap Cynfyn".
Trahaearn ruled Gwynedd until 1081, when Gruffydd ap Cynan returned from Ireland with an army of Danes and Irish and made an alliance with Rhys ap Tewdwr who had recently been ousted as prince of Deheubarth by Caradog ap Gruffydd of Morgannwg. Trahaearn countered by making an alliance with Caradog ap Gruffydd. He is also said to have had Norman arbalisters in his army, but at the Battle of Mynydd Carn, north of St David's, that year both Trahaearn and Caradog were killed, and Gruffydd ap Cynan took over the rule of Gwynedd while Rhys ap Tewdwr was restored as prince of Deheubarth. Trahaearn is recorded as having been killed by one of Gruffydd ap Cynan's men, an Irishman named Gucharki.
(Wikipedia)