Prestatyn castle was built by King Henry II in 1157. However, its history was only brief, spanning a mere ten years. The Welsh Prince Owain Gwynedd razed both the castle and the surrounding Norman town to the ground in around 1167, although it is said that part of the castle was still standing in 1297. Today, all that remains of the castle is a low mound, marked by a stone pillar.

Prestatyn castle consisted of a wooden tower standing on a motte (mound) of about 20m in diameter, surrounded by a ditch and defended by a bailey (outer defensive wall), probably made of wooden stakes sharpened at the top. The site of this Norman castle is just south of the railway line, close to the east side of Bodnant bridge (A548 coast road). Excavations carried out on the site in 1910 found foundation walls on three sides.

At the time of the castle's construction, the greater part of North Wales was held by the Welsh Princes - the most important of these being Owain ap Gruffydd or Gwynedd. He wanted to remove the Normans from their stronghold of Flintshire. However, he faced strong opposition from King Henry II, who, soon after his ascension to the throne in 1154, decided to advance westwards. After much battle, Owain Gwynedd was forced to make a temporary truce at Rhuddlan. It was at this point that Henry turned his attention to Prestatyn. He wanted to consolidate his position by building a castle to safeguard the strategic coastal route from Chester.

Robert Banastre (born in 1130 in Prestatyn) was charged with building Prestatyn castle. He was the mesne lord of the town. He enjoyed the castellary of Prestatyn for three and a half years, during which time he enlarged the township.

Henry's quarrel with Thomas a Becket, Archbishop of Canterbury, distracted his attention from the situation in Wales. The Welsh for once managed to unite under the leadership of Owain Gwynedd, and regained the territory they had earlier lost to Henry.

Thus, after an uneasy peace, Owain Gwynedd, aided by Rhys ap Gruffydd or the Lord Rhys, besieged Rhuddlan in 1167. Soon afterwards, Rhuddlan castle on Twt Hill was captured and destroyed. They then moved to the coast in the direction of Prestatyn, where they were determined to capture the castle.

At this time, Prestatyn was a small medieval commote, consisting of a number of cottages in the area around the castle, roughly between Nant Hall and Nant Mill. This small garrison, belonging to the Earl of Chester, was quite a busy little place for its size. It had its own market place, mill, blacksmith's shop and a granary. Some of its inhabitants, more adventuresome than the rest, put out to sea in small sailing boats, returning home with welcome catches of fish. Their boats were kept in a convenient harbour nearby on Prestatyn Gutter.

This strategic Norman garrison now faced the approaching Welsh armies under Owain Gwynedd. Its inhabitants were filled with fear as they saw the enemy advancing towards them along the edge of the marsh. Soon battle commenced, the air was filled with the clash and rattle of swords, the whistling, rushing sound of flights of arrows, the cries of the opposing forces locked in battle, the shrieks of the wounded and the groans of the dying. Even many of the women and children living here were killed during this fierce encounter. The battle was soon over, the Norman garrison was overwhelmed and proved no match for Owain Gwynedd's army. Owain immediately destroyed the castle, so that it would no longer stand guard on this strategic coastal route.

A period of peace now followed until 1195. From here onwards, at periodic intervals, the tide of war between the Welsh princes and the English monarchs swept backwards and forwards throughout the area.