Seisyllwg

Seisyllwg was a Welsh kingdom that existed in the 9th and 10th centuries. It was formed by the division of the earlier kingdom of Dyfed. The kingdom is traditionally said to have been founded by Seisyll ap Clydog. The precise extent of Seisyllwg's territory is not definitively known, but it is generally believed to have encompassed parts of southwest Wales, roughly corresponding to modern-day Pembrokeshire and Carmarthenshire.

The history of Seisyllwg is somewhat obscure, with limited contemporary sources. It was a turbulent period in Welsh history, marked by conflicts with neighboring kingdoms and incursions by Viking raiders. Seisyllwg likely existed in a state of shifting alliances and rivalries with other Welsh rulers.

In the late 10th century, Seisyllwg was absorbed into the larger kingdom of Deheubarth. This unification was largely achieved by Hywel Dda, who ruled over a significant portion of Wales. The legacy of Seisyllwg is primarily recognized through its place in early Welsh genealogies and historical accounts, contributing to the complex political landscape of medieval Wales. While the kingdom itself eventually ceased to exist as an independent entity, its name and the dynasty associated with it are preserved in historical records.