Pryderi fab Pwyll is an important character in Welsh mythology. He is the son of Pwyll and Rhiannon and became the king of Dyfed after his father died. He appears in all four parts of the Mabinogi, though his role changes in size and importance between stories. He is sometimes compared to Mabon ap Modron, a divine figure, and Jeffrey Gantz notes similarities between Pryderi and Peredur fab Efrawg, who is linked to the French figure Sir Percival de Galles.

Ifor Williams suggested that Pryderi might have originally been the main character of the Mabinogi as a whole, though some later scholars disagree with this idea.

Jeffrey Gantz describes Pryderi as "bold and enterprising, but rash to the point of foolishness." He also states that "his downfall, while pathetic, is not entirely undeserved."

Role in Welsh mythology

Pryderi was born in Arberth to Pwyll, the ruler of Dyfed, and Rhiannon, the daughter of Hyfaidd Hen. On the night of his birth, he disappeared while being cared for by six of Rhiannon's ladies-in-waiting. To avoid punishment, they spread dog's blood on a sleeping Rhiannon and claimed she had killed and eaten her baby.

Teyrnon, the ruler of Gwent Is Coed, had a mare that gave birth every year, but her foals always vanished. Teyrnon watched his stables and saw a strange creature with claws taking the foal. He cut off the creature's arm and found a child outside the stable. Teyrnon and his wife raised the boy and named him Gwri Wallt Euryn (meaning "Gwri of the Golden Hair") because his hair was as yellow as gold.

As Gwri grew, he matured much faster than normal, and he began to look more like Pwyll. Eventually, Teyrnon realized Gwri was actually Pryderi. The boy was reunited with Pwyll and Rhiannon and renamed Pryderi. He was then raised carefully by Pendaran Dyfed and became the most handsome and skilled young man in the kingdom.

After Pwyll's death, Pryderi became the ruler of the seven cantrefi of Dyfed. He expanded his lands by conquering Ystrad Tywi and Ceredigion. Later, he married Cigfa, the daughter of Gwyn Gohoyw, and combined the seven cantrefi of Morgannwg into his kingdom, though this conquest is not described in any texts.

Branwen, the sister of Bendigeidfrân, the king of Britain, was married to Matholwch, the king of Ireland. Branwen's half-brother, Efnisien, insulted Matholwch by harming his horses. Bendigeidfrân compensated Matholwch with new horses and a magical cauldron that could bring the dead back to life. After returning to Ireland, Branwen and Matholwch had a son named Gwern. However, Efnisien's insult caused trouble, and Branwen was mistreated. She sent a starling to warn Bendigeidfrân, who led an army to war against Ireland. Pryderi joined the battle.

The British army crossed the Irish Sea in ships, but Bendigeidfrân, who was very large, walked across the water. The Irish offered peace and built a house big enough for Bendigeidfrân, but they filled it with bags that seemed to hold flour but actually held armed soldiers. Efnisien discovered the trick and killed the soldiers by pressing their heads into the bags. Later, during a feast, Efnisien threw Gwern into a fire, causing a battle. He also destroyed the magical cauldron, sacrificing himself in the process.

Pryderi was one of only seven men to survive the battle. Bendigeidfrân, who was mortally wounded, told them to cut off his head and return it to Britain. The survivors stayed in Harlech, where Bendigeidfrân's head continued to speak. They later moved to Gwales, where they lived for eighty years without noticing the passage of time. Eventually, they returned to the world and buried the head on a hill facing France to protect against invasion.

Pryderi invited Manawydan, Bendigeidfrân's brother and a fellow survivor, to live with him in Dyfed. He arranged for Manawydan to marry Rhiannon. Soon after, Pryderi, Cigfa, Manawydan, and Rhiannon climbed a magical hill. When they returned, Dyfed had become a barren wasteland with no people. Pryderi and Manawydan traveled to England to earn a living but were forced to leave towns because other tradesmen resented their skills.

Returning to Dyfed, Pryderi and Manawydan went hunting and followed a white boar to a large fort. Against Manawydan's advice, Pryderi entered the fort and touched a golden bowl. His feet stuck to the ground, his hands stuck to the bowl, and he lost the ability to speak. Manawydan waited for Pryderi's return but eventually told Rhiannon of his disappearance. Rhiannon, upset with her son, also entered the fort and suffered the same fate. Pryderi, Rhiannon, and the fort vanished in a "blanket of mist."

Later, Manawydan freed them from their imprisonment. It was revealed that the enchanter Llwyd ap Cil Coed, who wanted revenge for an earlier insult, had caused their suffering. The enchantment over Dyfed was lifted.

Some time later, Pryderi received magical pigs from Arawn, king of Annwn. The pigs were stolen by Gwydion, a magician from Venedotia. Declaring war, Pryderi and his men fought Gwynedd. Both sides suffered heavy losses, but Math fab Mathonwy, king of Gwynedd, won and forced Pryderi to retreat. Pryderi was later killed in a duel with Gwydion at Y Velen Rhyd in Ardudwy. The men of Dyfed returned to their land, mourning their lost leader.

The Welsh Triads name