The Mabinogion is a collection of 11 prose stories collated from medieval Welsh manuscripts. These tales draw on pre-Christian Celtic mythology, international folktale motifs, and early medieval historical traditions. While some details may hark back to older Iron Age traditions, each tale is the product of a developed medieval Welsh narrative tradition, both oral and written.

Lady Charlotte Guest, in the mid-19th century, was the first to publish English translations of the collection, popularizing the name "Mabinogion". The stories appear in either or both of two medieval Welsh manuscripts: the White Book of Rhydderch (Llyfr Gwyn Rhydderch), written around 1350, and the Red Book of Hergest (Llyfr Coch Hergest), written between 1382 and 1410. Texts or fragments of some tales have been preserved in earlier 13th-century and later manuscripts.

Scholars agree that the tales are older than the existing manuscripts, but there is debate over just how much older. The different texts originated at different times. Debate has focused on the dating of the Four Branches of the Mabinogi. Sir Ifor Williams offered a date prior to 1100, based on linguistic and historical arguments, while later, Saunders Lewis set forth arguments for a date between 1170 and 1190. Th Charles-Edwards, in a paper published in 1970, discussed both viewpoints and noted that the language of the stories fits the 11th century. More recently, Patrick Sims-Williams argued for a plausible range of about 1060 to 1200, which is the current scholarly consensus.