This book provides a comprehensive overview of Celtic mythology and religion, encompassing numerous aspects of ritual and belief. Topics include the presence of the Celtic Otherworld and its inhabitants, cosmology and sacred cycles, wisdom texts, mythological symbolism, folklore and legends, and an appreciation of the natural world. Evidence is drawn from the archaeology of sacred sites, ethnographic accounts of the ancient Celts and their beliefs, medieval manuscripts, poetic and visionary literature, and early modern accounts of folk healers and seers. New translations of poems, prayers, inscriptions and songs from the early period (Gaulish, Old Irish and Middle Welsh) as well as the folklore tradition (Modern Irish, Scottish Gaelic, Welsh, Cornish, Breton and Manx) complement the text. Information of this kind has never before been collected as a compendium of the indigenous wisdom of the Celtic-speaking peoples, whose traditions have endured in various forms for almost three thousand years.