Situated at a strategic point on the lowest crossable point of the River Clwyd, fortifications at Rhuddlan can be traced back to the 8th century.
In 1073 a Norman motte and bailey rose over the ruins of an old Welsh fort. It was founded by Robert of Rhuddlan, deputy of the Earl of Chester. Remnants of the motte and bailey can be seen to the south of the present castle.
The fortification was still wooden and changed hands many times during border skirmishes. During the reign of Henry III, Llywelyn ap Gruffydd, Prince of Wales, finally united all the princes of the north under him and began to enlist baronial support in Wales. However, when he tried to defy the new king, Edward I, a new era began for Rhuddlan Castle.
In 1277 Edward marched into Wales and having started building Flint Castle he moved to Rhuddlan. Llywelyn surrendered and submitted to the King's uncompromising peace terms at Rhuddlan. Edward immediately set about building a castle. In charge of the design and construction was the King's master builder, James of St. George. The castle was concentric, although now most of the outer polygonal walls have disappeared. The inner walls were diamond-shaped with two double-towered gatehouses set at diagonally opposed corners and single round towers on the other two corners. The castle was ringed by a moat.
The town was defended by earthworks and timber built between 1280 and 1282. Edward wanted the castle to have access to the sea and so a new channel was dug that was straighter and deeper than the existing river. The huge project took three years to complete and today the river still follows the new course.
Rhuddlan Castle was the Edward I's headquarters during both Welsh campaigns. In 1282 the main defences were complete when Llywelyn's brother Dafydd, with the Prince's support, headed a new Welsh uprising. The Welsh attacked Rhuddlan but with no success and by the end of the year Llywelyn had been killed and Dafydd captured and executed at Shrewsbury.
In the 15th century the town was ravaged during Owain Glydwr's revolt but apart from that episode the castle had a peaceful existence as a centre of Welsh administration until the Civil War. The castle was garrisoned for the Charles I but in 1646 surrendered to the Parliamentarians. In 1648 the castle was slighted by order of Parliament.
The castle continued to decay until guardianship passed to the Government in 1948 and restoration began.