Oystermouth Castle was built by Norman invaders who sought to conquer the Gower peninsula. It was attacked and burnt on multiple occasions by the native Welsh but was regularly rebuilt. In the thirteenth century it became the primary residence of the de Braose family and remained an important site until the mid fourteenth century.



In the early twelfth century Wales was a series of independent Kingdoms whose power and influence fluctuated depending upon the strengths of their respective rulers. Whilst there was no centrally co-ordinated Norman invasion of Wales, various magnates were encouraged to seize land within the Principality and in return these so-called Marcher Lords were given near regal powers within their new territories. As part of this piecemeal conquest of South Wales, Henry I granted the Gower peninsula to Henry de Beaumont, Earl of Warwick in 1107. He invaded and immediately built Swansea Castle. He also granted land on the peninsula to his supporters and the area around Mumbles was granted to William de Londres, a Norman Knight who also owned Ogmore Castle. Soon after being granted his new lands, William built Oystermouth Castle on a hill overlooking Swansea Bay. The initial structure was probably an earth and timber ringwork fort.


Perhaps unsurprisingly given it had been seized from them, the Gower peninsula was hotly contested with the native Welsh. In 1116 Gruffydd ap Rhys invaded Gower and burnt the castle. The Normans rebuilt it but in 1136 Gower was again invaded by the Welsh, this time by Hwyel ap Maredudd, and it is possible Oystermouth was destroyed once more. Further attacks on the peninsula occurred in 1189 and 1192 (both by Lord Rhys of Dehebarth) although the castle seems to have survived in both instances.


In 1203 King John granted the Lordship of Gower to John de Braose although Oystermouth Castle remained the property of the Londres family. The male line of the that family failed in 1215 and the castle then reverted to William de Braose as Lord of Gower. Around the same time Oystermouth Castle was once again attacked by the Welsh led by Rhys Grug and Rhys Ieunanc, both allies of Llywelyn ap Iorwerth.


The de Braose family were at the forefront of national politics and in the late thirteenth century made Oystermouth Castle their primary residence. Around this time the castle was rebuilt in stone most probably by William de Braose, Baron Braose. William was a powerful magnate within Edward I's court and hosted the King at Oystermouth Castle in December 1284. He also served with the Edward's forces in both his Welsh and Scottish wars with his notable achievements being the capture of the Welsh rebel William Cragh in 1290 and participation in the Battle of Falkirk (1298) where Royal forces defeated William Wallace.


The last major additions to the castle were made by Alina de Braose who built the chapel block. In 1331 it passed to her son, John de Mowbray, who was the first in a long line of absentee owners. The fabric of the castle was allowed to decay and therefore it played little part in the rebellion of Owain Glynd┼Ár, who occupied the Gower peninsula between 1403 and 1405, and over the subsequent centuries it passed through multiple owners before being placed in State care in 1927.




Draisey, D (2002). A History of Gower. Logaston Press.

Ferris, P (2009). Gower in History. Armanaleg Books.

Gower Society (2005). The Castles of Gower. Gower Society

Kenyon, J (2010). The Medieval Castles of Wales. University of Wales Press, Cardiff.

King, C.D.J (1983). Castellarium anglicanum: an index and bibliography of the castles in England, Wales and the Islands.  Kraus International Publications.

Reeves, A.C (1983). The Marcher Lords. Christopher Davies Publishers.

Turvey, R.K (2014). The Marcher Lords.  Gwasg Carreg Gwalch.

Williams, D.M (1995). Weobley Castle. CADW, Cardiff.

Williams, D.M (1998). Gower: A Guide to Ancient and Historic Monuments on The Gower Peninsula. CADW, Cardiff.

What's There?

Oystermouth Castle consists of the ruins of a small but impressive Norman castle. The bulk of the remains visible date from the thirteenth and fourteenth centuries but the site was used much earlier. The castle walls give fantastic views over Swansea Bay.

Gower Peninsula. The Norman invasion of Gower was led by Henry de Beaumont, Earl of Warwick in the early twelfth century. He and his followers built multiple castles on the Gower peninsula most notably at Swansea, Loughor, Oystermouth, Penrice, Penmaen and Pennard.

Gatehouse. The twin-towered gatehouse was built in the late thirteenth century probably by William de Braose, Baron Braose. Its strange appearance is due to the later demolition of the outer walls of the round towers that once flanked the passageway.

Swansea Bay. The view of Swansea Bay and the Mumbles from the castle.

Getting There

Oystermouth Castle is found of the A4067 coastal road and is well sign-posted as you approach the Mumbles. There are a few car parking spaces in immediate vicinity of the castle but the main car park is shown below.

Car Park

Mumbles Road, SA3 4DN

51.575131N 3.998211W

Oystermouth Castle


51.576964N 4.002700W