Lady Charlotte Guest publishes 'The Mabinogion,' the first complete English translation of medieval Welsh prose tales derived from oral traditions of the Mabinogi, containing Arthurian folklore, Celtic otherworld mythology (Annwn), shape-shifting, and magical animals. The 12 tales preserve pre-Christian enchantment logic, cauldron rebirth rituals, and bardic memory practices from 11th-13th century manuscripts.

The Mabinogion's translation profoundly influenced 19th-century British poets (Tennyson's Idylls of the King, Matthew Arnold's Celtic literature lectures) and 20th-century Welsh poets (R. S. Thomas, Gillian Clarke), who adapted Annwn imagery, wild folklore, and bardic genealogy structures into English- and Welsh-language poetry against rural depopulation and Anglicization. The stories' 'four branches' and their folkloric repetition patterns provided narrative models for contemporary long poems (John Ashbery's 'Flow Chart'). The Mabinogion proves that prose folklore translations generate poetic movements when they provide alternative mythic geographies to classical ones.