Prince Llywelyn of Gwynedd's favourite dog is Gelert, a fearless hunting dog and loyal friend and companion who was said to have been a gift from King John of England.
Llywelyn leaves his baby son with a nurse and a servant while he embarks on a hunting trip with his wife. The nurse and the servant go for a walk in the mountains leaving the baby alone and unprotected. After a while Llywelyn notices that Gelert isn't with the hunting pack. Reasoning that the only place Gelert would go is back to the lodge, he calls off the hunt and heads back home.
As the party is dismounting, Gelert comes running out of the lodge towards his master, covered in blood and wagging his tail. The princess, calling her child's name, faints. Llewelyn rushes in to find the cradle overturned, the bloodstained bedclothes thrown all over the floor, and no sign of his son.
Filled with anger and grief he draws his sword against the dog. As Gelert dies, he whimpers and his cries are answered by the sound of a baby crying from behind the overturned cradle. Llewelyn pulls aside the cradle to find his son unharmed and the bloody body of a huge wolf next to him. Gelert had killed the wolf as it tried to attack Llewelyn's son.
From that day onwards Llewelyn never speaks again. Filled with remorse, he buries Gelert in a meadow nearby and marks the grave with a cairn of stones, though he could still hear its dying cries.
The village of Beddgelert (Gelert's grave) in North West Wales is thought to owe its name to the legend, although there is no evidence of the story having a historical basis.