According to Irish mythology, the Tuatha Dé Danann were the fifth race of people to settle in Ireland. According to Irish mythological history, they were the inhabitants of Ireland when the Milesians, thought to be the Celtic-speaking Gaels, arrived.
The Tuatha Dé Danann represent mythical inhabitants of Ireland and include a number of heroes in Irish stories. It is believed that the story of the Tuatha Dé Danann originally counted the group as dieties, and a number of old Irish-Celtic gods appear in demoted forms as Tuatha Dé Danann. It is likely that they emerged in this form after Christianity spread throughout Ireland and reduced the earlier religion to folk tales and mythical history.
The name Tuatha Dé Danann roughly means “people of the goddess Danu”. Danu was seen as the mother goddess of this race, but may have also been a goddess worshipped elsewhere in the Celtic world, and perhaps in other religions of Indo-European origin.
Much of the mythical history of this group comes from the Lebor Gabála Érenn, the Book of Invasions from the Mythological Cycle.