There are some 100 castles in Carmarthenshire. Most of these are early earth and timber fortifications, mottes and ringworks, most of which were only in use for short periods. The rest are massive stone fortresses, important centres of Norman and English power.

The death of King Rhys ap Tewdwr in battle in AD 1093 allowed the Normans to invade his kingdom. The invaders faced strong native resistance and, in the 12th century, Carmarthen was divided between a Welsh heartland and a number of Norman lordships centred on Kidwelly, Llansteffan, Laugharne, St Clears and Llandovery. Carmarthen was the king of England’s power base, allowing him to keep an eye on both the Welsh population and on the ambitious marcher (border) lords in the south-west. Welsh princes also built stone castles to secure their own lands at Carreg Cennen, Dinefwr, Dryslwyn and Newcastle Emlyn.

The Anglo-Normans established towns around major castles, from which they exerted economic control over their new lands. They introduced manors, feudal organisation of land holding and the three-field farming system, as well as churches and parishes organised on Norman patterns. The Anglicised lordships along the coast flourished and their traces can still be seen in the landscape. Welsh princes followed the Normans, building their own small towns.