- Seisyllwg
Seisyllwg was a kingdom of medieval
South Wales , covering the areas now known asCeredigion , part ofCarmarthenshire , and theGower peninsula .Origins
Seisyll (born c. 665) was a direct descendant of King Ceredig's eldest son,Usai . He was a late 7th century king ofCeredigion who invadedDyfed and managed to conquerYstrad Tywi . His enlarged kingdom of Ceredigion and Ystrad Tywi became known as Seisyllwg in his honour.Expansion and Merger with Dyfed
By
800 , the kingdoms ofBuilth andGwerthrynion were united through intermarriage and conquest with SeisyllwgFact|date=August 2007.Historical Chronology of early British kingdoms [http://www.earlybritishkingdoms.com/kingdoms/805.html]The kingdom passed to
Rhodri Mawr , the King ofGwynedd , in872 , and was from then onwards ruled by a branch of his family. In920 ,Hywel Dda merged Seisyllwg with Dyfed to create the Kingdom ofDeheubarth . From this power base, he later went on to unite almost all of Wales.
Wikimedia Foundation. 2010.