Mabinogion
The Mabinogion is a collection of eleven anonymous tales written in Welsh during the eleventh, twelfth, and thirteenth centuries. Like much of ancient Irish literature, this material offers evidence of pre-Christian Celtic religion. The oldest tales, known as the four branches, develop fundamental aspects of Celtic mythology, focusing on the lives and deeds of certain mythical figures. Some of these heroes represent the deities of the ancient Celts.