The Celts and Their Influence on Irish Mythology

Irish mythology goes far beyond leprechauns and banshees.

The rich heritage of gods, goddesses, fairies, and monsters dates back to the Celts, the people who lived in central and western Europe 14,000 years ago during the Iron Age.  

Europe, 1,000–500 BC

To place the origins of this culture in perspective, consider that the first humans walked the earth 2.5 million years ago. According to, there were somewhere between a half and one million people on Earth when the Celts first evolved as a distinct culture. By 7,000 BC, that number more than doubled.

Celts in Prehistory

Celtic and Irish history are well-represented in prehistoric human development. Consider these dates:

300,000 BC Middle Stone Age
20,000 BC Cro-Magnons paint caves with drawings of the animals they killed
16,000 BC Celts evolve as a distinct culture in central and western Europe
8,000 BC Ireland’s earliest inhabitants arrive in wooden boats from Scotland, to what is now County Antrim
6,500 BC Ice Age ends and seas rise, separating England from Europe. Coincides with archeological estimate of Noah’s flood.
4,250 BC Copper and bronze are developed
4,000 BC The wheel is invented
3,200 BC Newgrange, Ireland’s most famous prehistoric site, is built
3,100 BC Stonehenge construction begins
2,550 BC First Egyptian pyramid construction begins
1,000 BC Celts (Gaels) arrive in Britain

Celtic Religion

As with other ancient cultures, the Celts’ polytheistic religion was based on deities associated with natural phenomena. Lugh, for example, whose name means Shining One, was the sun god.

The Celts, however, did not write this down. Nor did they write about themselves. Nor did they even name themselves. The Greeks and Romans did all that. The Greeks called them Keltoi, Keltai or Galatai; the Romans, Celti, Celtae and Galli.

Since Celtic culture originated in central Europe, not all Celtic mythology is Irish—but all Irish mythology is Celtic in origin. Although the Romans imposed their culture everywhere they conquered, they never got to Ireland.

Celts in Ireland

The Celts—Gaels (from whom the word Gaelic is derived)—arrived in Britain around 1,000 BC and in Ireland 300 to 500 years later. But they were far from Ireland’s first inhabitants. The indigenous people’s presence dates to at around 8,000 BC, with some estimates as early as 31,000 BC.

Upon reaching Ireland, the Gaels encountered massive stone structures (dolmens and cairns) and earthen burial mounds (tumuli), which inspired new stories and beliefs that were incorporated onto their existing polytheism. The burial mound at Newgrange, for example, was believed to be a portal to the Celtic Otherworld.

Irish Mythology

Irish mythology differs from that of many other cultures because there is no creation element. It always existed.

Dancing Fairies by Richard Doyle, 1824-1883

Its foundational tales are divided into four distinct chronological phases, or cycles: Mythological, Ulster, Fenian, and Kings.

The Mythological Cycle is subdivided by “waves” of colonization, based on two sources: Lebor Gabála Érenn (also known as The Book of the Taking of Ireland, or The Book of Invasions) and Metrical Dindshenchas (Lore of Places). Both were written by Christian monks between the 10th and 14th centuries AD, and thus seem to be attempts to blend Ireland’s pagan history with Biblical accounts.

According to the Mythological Cycle, the colonizers were:

Partholanians. A hospitable and productive people, the Partholonians cleared the land, formed the lakes, introduced agriculture, divided the island into four parts, established laws, brewed ale, and made crafts. They lived in Ireland for three hundred years, and battled with the Fomorri. They were mysteriously wiped out by a plague.

Fomorri. Hideously misshapen, with only one eye, one arm, and one leg, the Fomorri were ugly giants, who were cruel, violent, and oppressive. They lived mainly in the sea.

Nemedians. Following a short-lived dominance by Nemed of Scythia, the Nemedians lost the battle of Tory Island and fled Ireland. Nemed then lost his fleet at sea.

Fir Bolg. The name means Men of the Bags and refers to the leather bags of earth they carried. The Fir Bolg were probably escaped Greek slaves. They were conquered by the Tuatha Dé Dannan.

Tuatha Dé Dannan (Fairy-Folk): Often depicted as kings, queens, druids, bards, warriors, heroes, healers, and craftsmen, the Tuatha Dé Dannan’s were believed to have supernatural powers in addition to their wisdom, divinity, and beauty.

Milesians: The final race to settle in Ireland, the Milesians were Gaels who sailed to Ireland from Iberia after spending hundreds of years looking for the land they believed God had promised them—an island toward the setting sun where no venomous reptile lived. As the first Celts, they drove the Tuatha Dé Danann underground to rule the Otherworld, leaving the world above to them.

Next Month—The Gods and Goddesses

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