Llywelyn ap Seisyll, King of Wales

Llywelyn ap Seisyll was a king of Gwynedd in the 11th century who ruled over the Welsh kingdoms of Gwynedd, Powys, and Deheubarth. He was the son of Seisyll and Prawst, with his maternal lineage tracing back to Anarawd ap Rhodri, a former King of Gwynedd. Llywelyn was married to Angharad, the daughter of Maredudd ab Owain ap Hywel Dda, who had previously ruled in the same regions.

In 1018, Llywelyn defeated and killed Aeddan ap Blegywryd and his four sons, gaining control of Gwynedd and Powys. In 1022, he contested the claim of Rhain the Irishman to Deheubarth, as Rhain claimed to be a son of Maredudd ab Owain. After a battle at Abergwili, where both sides suffered casualties, Llywelyn emerged victorious and took control of Deheubarth.

Llywelyn died in 1023, with no specific cause of death mentioned. His son, Gruffydd ap Llywelyn, did not immediately succeed him, possibly due to his young age at the time.