The Mabinogion is a medieval Welsh document, consisting of eleven stories. The Mabinogion was named that by translator Charlotte Guest; the texts come from two Welsh story collections from the 14th century called the White Book of Rhyderch, written down between 1300-1325, and the Red Book of Hergest, written down between 1375 and 1425.
The stories are varied, but they include a hero's tale, and the earliest known reference to a King-Arthur-like person. Similarities between some of the stories in the Sanskrit Mahabharata have been noted; which proves just how far a really good story can travel, given half a chance.
Parts of the Mabinogion were first published in English by William Owen Pughe in 1795; Lady Charlotte Guest published all of the stories, along with The Taliesen, in 1838-1849. The 1947 version of the Mabinogion, translated by Gwyn and Thomas Jones, is available as part of Google Books. It has an extensive introduction worth reading.
Sources
Several versions of the Mabinogion are available on the internet:
Guest, Lady Charlotte. 1877. The Mabinogion. Google Books
Jones, Gwyn and Thomas Jones. 1947. Mabiongion. Read books, printed 2007. ISBN 1408633752, 9781408633755 316 pages
Parker, Will. 1977. The Four Branches of the Mabinogi. Mabinogi.net
