Hyfaidd ap Bleddri (born c. 830) was a king of Dyfed.
[1] His mother was supposed to be Tangwystl, a daughter of the earlier King Owain.
Charles-Edwards argues that Hyfaidd was responsible for consolidating the lands that would later become Deheubarth, annexing Ystrad Tywi and possibly Ceredigion to Dyfed before his death.
[2] He was said to have oppressed the clerics of Meneva (modern St. David's)[3] and exiled Bishop Nobis,[4] earning him the enmity of Nobis's kinsman, the historian Asser.
Although later Welsh histories made Hywel Dda's inheritance of Dyfed a peaceful affair brought about by his marriage to Hyfaidd's granddaughter Elen and the extinction of Hyfaidd's male line, Asser's more contemporary Life of King Alfred reports that Dyfed or Brycheiniog both fell under such sustained attack from Hywel's uncle Anarawd and father Cadell that Kings Hyfaidd and Elise submitted to King Alfred of Wessex's overlordship in exchange for protection.