The following introduction is taken in part from "The Mabinogion" translated by Jeffrey Gantz.

The tales of the Mabinogion are not the product of a single hand. They evolved over a span of centuries: passed on from storyteller to storyteller, they were distorted, improved, and misunderstood. The people responsible for The Mabinogion are the Welsh who are descendants of the Celts. Its contents draw upon the myths, folklore, history and pseudo-history of Celtic Britain: four well-springs that are often indistinguishable. Set largely within the British Isles, the tales create a dreamlike atmosphere and preserve much of the primitive, fantastic, fascinating world of Celtic myth. They exemplify the heroic, romantic, idealistic world of Celtic literature.