Celtic mythology is the body of myths, gods and heroic legends of the Celtic-speaking peoples of ancient and medieval Europe. It is known from Greek and Roman writers, inscriptions and images from Gaul and Britain, and above all from medieval Irish and Welsh literature, which preserved stories of the Tuatha De Danann, Cu Chulainn, Fionn mac Cumhaill and the Mabinogi.
Celtic Mythology at a glance
| Peoples | Celtic-speaking peoples of Iron Age Europe and their medieval successors |
|---|---|
| Main sources | Classical writers, inscriptions and images, medieval Irish and Welsh manuscripts |
| Irish cycles | Mythological, Ulster, Fenian and Kings' Cycles |
| Welsh collection | Four Branches of the Mabinogi |
| Well-known figures | The Dagda, Lugh, Brigid, the Morrigan, Cu Chulainn, Fionn mac Cumhaill |
| Seasonal festivals | Samhain, Imbolc, Beltane, Lughnasadh |
Sources and Their Problems
The ancient Celts left few written texts of their own; druidic learning was passed on orally. As a result, Celtic mythology has to be pieced together from three kinds of evidence. First are Greek and Roman authors such as Julius Caesar, Lucan and Tacitus, who described Celtic religion from the outside and often in hostile or stereotyped terms. Second are archaeological finds: dedications to gods, statues, coins and sacred sites across Gaul, Britain and beyond. Third, and richest, are the medieval literatures of Ireland and Wales.
Those medieval stories were written down by Christian scribes, mostly monks, centuries after conversion. They preserve much older material, but it was reshaped by Christian learning and literary taste, so scholars are cautious about reading them as direct records of pagan belief.
Gods of the Continental Celts
Caesar wrote in his Gallic War that the god the Gauls honored most was one he called Mercury, the inventor of all arts. Roman writers routinely gave foreign gods Roman names, so the native identity is uncertain, though many scholars link this figure with Lugus, whose name appears in place names such as Lugdunum (Lyon). Lucan mentions the gods Teutates, Esus and Taranis.
Inscriptions and images reveal hundreds of other deities, many local. Among the best known are Epona, a horse goddess worshipped even by Roman cavalry, and the antlered god named Cernunnos on the Pillar of the Boatmen in Paris. A similar antlered figure appears on the silver Gundestrup cauldron found in Denmark. Springs, rivers, groves and lakes were widely treated as sacred.
Irish Mythology
Ireland preserves the largest body of Celtic mythological literature. The Mythological Cycle and the Lebor Gabala Erenn (Book of Invasions) tell of successive peoples who settled Ireland, including the Tuatha De Danann, a race of gods led by figures such as the Dagda, Nuada, Lugh and the goddesses Brigid and the Morrigan. After their defeat by the ancestors of the Gaels, the Tuatha De Danann withdrew into the hills and mounds, the sidhe, becoming the ancestors of the fairy folk of later tradition.
The Ulster Cycle centers on the hero Cu Chulainn and the epic Tain Bo Cuailnge (The Cattle Raid of Cooley). The Fenian Cycle follows Fionn mac Cumhaill and his warrior band, the Fianna, while the Kings' Cycle concerns legendary and semi-historical kings.
Welsh Mythology
In Wales, the most important source is the collection of medieval tales known in English as the Mabinogion, especially the Four Branches of the Mabinogi. They tell of Pwyll, lord of Dyfed, and his otherworldly bride Rhiannon, of the giant king Bran the Blessed, and of magicians such as Math and Gwydion. Other tales, such as Culhwch and Olwen, contain some of the earliest Arthurian material. Lady Charlotte Guest's nineteenth-century English translation made them known to a wide audience.
Druids, Festivals and Belief
Classical writers describe the druids as a learned class of priests, judges and teachers. Caesar reports that they taught that souls do not perish but pass from one body to another after death, a claim often compared with reincarnation. The medieval Irish calendar was marked by four great festivals: Samhain at the start of winter, Imbolc, Beltane at the start of summer, and Lughnasadh at harvest. Samhain, when the boundary with the otherworld was thought to be open, later influenced the customs of Halloween.
Legacy and Modern Revival
From the eighteenth century onward, Romantic writers, antiquarians and nationalists rediscovered Celtic myth. The Irish literary revival of W. B. Yeats and Lady Gregory drew heavily on it, and modern Druidry and Celtic Paganism draw on the old stories today. Writers such as Lewis Spence popularized Celtic themes in occult circles, often with more imagination than evidence. Scholars continue to separate what can be known about ancient Celtic religion from later romantic reconstruction.
Celtic themes also shaped Arthurian romance, fantasy fiction and popular ideas of fairy lore, sacred wells and holy places. For many people in Ireland, Scotland, Wales, Brittany, Cornwall and the Isle of Man, the old stories remain part of a living cultural heritage.
Related entries
Frequently asked questions
Who are the main Celtic gods?
Well-known Irish deities include the Dagda, Lugh, Brigid, Nuada and the Morrigan, members of the Tuatha De Danann. In Gaul and Britain, inscriptions and images name gods such as Lugus, Epona, Cernunnos, Taranis and many local deities of springs and places.
Where does Celtic mythology come from?
It comes from classical Greek and Roman descriptions, archaeological evidence such as inscriptions and statues, and medieval Irish and Welsh manuscripts written by Christian scribes. Because the Celts themselves relied on oral tradition, all these sources must be interpreted with care.
What is the connection between Samhain and Halloween?
Samhain was the medieval Irish festival marking the start of winter, when the boundary between this world and the otherworld was thought to be thin. Many Halloween customs in Ireland and Scotland developed from Samhain traditions, blended over time with the Christian feast of All Saints.
Sources and further reading
This entry replaces an article from the original Mystica encyclopedia (online since 2001). It was rewritten from the sources above by The Mystica Editorial Team under our editorial standards. Last reviewed: September 30, 2026.