Like other Iron Age Europeans, the early Celts maintained a polytheistic mythology and religious structure. Among Celts in close contact with Ancient Rome, such as the Gauls and Celtiberians, their mythology did not survive the Roman Empire, their subsequent conversion to Christianity, and the loss of their Celtic languages. It is mostly through contemporary Roman and Christian sources that their mythology has been preserved. The Celtic peoples who maintained either their political or linguistic identities (such as the Gaels in Ireland and Scotland, and the Celtic Britons of southern Great Britain and Brittany) left vestigial remnants of their ancestral mythologies, put into written form during the Middle Ages.

"Celtic Myths and Legends" is a masterful retelling of some of these stories, including Irish and Welsh tales of the Ultonian and Ossianic cycles, the voyage of Maeldun, and the myths and tales of the Cymry. Favorite and familiar stories of Cuchulain, King Arthur, Deirdre, the Grail, and many more.