Seisyllwg

Kingdom of Seisyllwg
Teyrnas Seisyllwg (Old Welsh)
680–920
Medieval kingdoms of Wales
Medieval kingdoms of Wales
Common languagesWelsh
GovernmentMonarchy
Historical eraMiddle Ages
• Changed name from Ceredigion
680
• Union with Dyfed forming Deheubarth
920
Preceded by
Succeeded by
Kingdom of Ceredigion
Deheubarth
^

Seisyllwg (Welsh: [sɛiˈsəɬʊɡ]) was a petty kingdom of medieval Wales.[1] It is unclear when it emerged as a distinct unit, but according to later sources it consisted of the former Kingdom of Ceredigion plus the region known as Ystrad Tywi. Thus it covered the modern county of Ceredigion, part of Carmarthenshire, and the Gower Peninsula. It is evidently named after Seisyll, king of Ceredigion in the 7th or early 8th century, but it is unknown if he was directly responsible for its establishment. In the 10th century Seisyllwg became the centre of power for Hywel Dda, who came to rule most of Wales. In 920 Hywel merged Seisyllwg with the Kingdom of Dyfed to form the new kingdom of Deheubarth.

  1. ^ Davies, p. 85