Elen ferch Llywarch
- Born: Abt 885, Dyfed, Wales
- Marriage (1): Hywel Dda King of Deheubarth
- Died: 943 about age 58
From A History of Wales by John Davies, London, 2007, p. 83:
"If the intention of the rulers of Dyfed and Brycheiniog in seeking the patronage of Alfred was to remain free from the clutches of the house of Rhodri, they failed. About 904, Llywarch ap Hyfaidd, king of Dyfed, died; his kingdom came into the possession of Hywel [Dda] ap Cadell ap Rhodri, the ruler of Seisyllwg and the husband of Elen, Llywarch's daughter. It would appear that Hywel also took possession of Brycheiniog, for its royal line ends with Tewdwr ap Griffri, who died about 930. The enlarged kingdom came to be known as Deheubarth, a unit of central importance in the history of Wales during the following four centuries."
Elen married Hywel Dda King of Deheubarth, son of Cadell ap Rhodri Mawr King of Seisyllwg and Rheingar. (Hywel Dda King of Deheubarth was born circa 880 in Dinefwr Castle, Llandeilo, Carmarthenshire, Wales and died about 950.)