A medieval Welsh kingdom named after its founder Ceredig, which pursued an independent existence until the late ninth century after which was at various times incorporated into Gwynedd, Deheubarth and Powys.
The Kingdom of Ceredigion
From the Welsh Genealogies is derived a list of the rulers of independent Ceredigion which begins with Ceredig the alleged founder and fifth son of Cunedda and proceeds as follows;
We can fairly reasonably place Seisyll ap Clydog in the mid to late eighth century, as the genealogy given, extends forwards to his descendants Arthgen and Gwrgan who can be dated with a reasonable accuracy.
The real problem with this list is that it is too short; seven generations back from that is some 210 years, which would place Ceredig ap Cunedda some time in the mid sixth century about a 100 to 150 years to late for a supposed son of Cunedda. The comparable genealogy for the line of Gwynedd whose descent was similarly traced from Einion Yrth the seventh son of Cunedda, is three generations longer. Some seek to resolve this inconsistency by postulating a 'gap' in the sequence of the kings of Cerdigion somewhere or other, but the more obvious and sensible conclusion is that the claimed descent from Cunedda is a later invention to designed to strengthen the claims of the line of Merfyn Frych over Ceredigion.
The Kingdom of Seisyllwg
It was during the reign of Seisyll that Ceredigion conquered Ystrad Tywi and the newly enlarged kingdom re-named as Seisyllwg, although how prevalent was the comtemporary use of this new label is unclear as the Annales Cambriae continued to refer to kings of Ceredigion.
Ceredigion/Seisyllwg lost its independence in the late ninth century; Gwrgan ap Meurig, the great-grandson of Seisyll ap Clydog, died very probably at the hands of Rhodri Fawr of Gwynedd in 862, and Rhodri's son Cadell had the kingdom firmly in his grasp a generation later.
It was Cadell's son Hywel Dda who took control of both Dyfed and Seisyllwg and forged the new identity of Deheubarth in around 950.
The Sub-Kingdom of Ceredigion
Ceredigion remained firmly part of Deheubarth until the after the death of Rhys ap Tewdwr in 1093 when it fell under the control of the Normans (as did most of Wales at the time.)
In 1099 after the conclusion of the First Anti-Norman rebellion, Ceredigion passed under the control of Cadwgan ap Bleddyn of Powys, but after his death and the subsequent decline and eventual fragmentation of Powys, his successors were unable to exercise any authority over the region.
In any event Cadwgan's determined resitance to Norman authority, led Henry I in 1110 to authorise Gilbert Fitz Richard of Clare to take control of Ceredigion if he could. By this time the Normans had firmly entrenched themselves in southern Dyfed and an extension of their control into northern Dyfed and Ceredigion was the next logical step.
Gilbert Fitz Richard built castles at Cardigan and Aberystwyth but Owain Gwynedd brought Ceredigion under the control of Gwynedd only to see it slip back again into the hands of the grandsons of Rhys ap Tewdwr and more specifically Rhys ap Gruffudd. For most of the twelfth century control switched between Deheubarth and the Norman de Clare family until Deheubarth faded from the picture after the death of Rhys ap Gruffudd, the Lord Rhys in 1196.
Thereafter it remained a territory disputed between the kings of England and the Venedotian Princes of Wales until the final conquest of Wales by Edward I in 1283.
Ceredigion was transformed into the shire county of Cardiganshire after the Acts of Union 1536-1543, although it continued to be known in the Welsh as 'sir Ceredigion' or sometimes 'sir Aberteifi'.
In 1974 Cardiganshire disappeared into the super-county of Dyfed, only to re-emerge once more following the local government re-organisation of 1996. Cardiganshire however remains one of the more Welsh speaking parts of the country and the new county council therefore re-named itself as the county of Ceredigion.