Gruffudd ap Cynan was born in Dublin to a Norse mother, Ragnell, and a Welsh father, Cynan, through whom he traced his ancestry back to the great 9th-century Welsh ruler Rhodri Mawr. His grandfather Iago had been King of Gwynedd until his murder in 1039, and in 1075 Gruffudd set sail from Dublin with an Irish army to claim his birthright.
After some initial successes against Traehearn ap Caradog (another claimant to the throne of Gwynedd), Gruffudd retreated to Ireland. He returned in 1081, however, with a combined Scandinavian and Irish force. He fought and killed Traehearn in the Battle of Mynydd Carn and took the throne of Gwynedd for a second time.
Not long after, apparently through the treachery of one of his own men, Gruffudd was imprisoned for several years by Hugh of Chester, a Norman earl. After a dramatic escape he fled to Ireland once more, then returned to spearhead the Welsh resistance to the Normans (who now controlled large parts of north Wales). Ireland once more offered refuge in 1098, but the following year Gruffudd returned yet again to Gwynedd, where he remained until his death. With the help of King Magnus III of Norway, the Normans were forced out of north Wales. In 1101 Gruffudd came to an agreement with King Henry I of England, which granted him sovereignty over much of Gwynedd.
The Gwynedd of Gruffudd’s reign was described as “bespangled with lime-washed churches like the stars in the firmament”. It was a golden age, a time of political stability and prosperity. Gruffudd rebuilt Bangor Cathedral, which had been destroyed by Vikings in 1073. He died at the age of 82 and was buried at the high altar there.