Ancient Celtic religion, also called Celtic paganism, was the belief system of the ancient Celtic people who lived in Europe. Since no written records from the Celts themselves have survived, information about their religion comes from archaeological findings, writings by Greek and Roman authors (some of whom may not have understood the Celts well), and texts from the early Christian era. Celtic paganism was part of a larger group of religions in Iron Age Europe that worshipped many gods.

Although the gods worshipped by the Celts changed over time and in different regions, there were common similarities among their beliefs and a general religious unity among Celtic people. Many gods were widely honored, including Lugus, Toutatis, Taranis, Cernunnos, Epona, Maponos, Belenos, and Sucellos. Sacred springs were often linked to gods associated with healing. The idea of triplicity, or three parts or forms, was common, such as the "Three Mothers" who were seen as threefold.

The druids were the religious leaders of the Celts, but not much is known for sure about them. Greek and Roman writers described Celtic ceremonies held in sacred groves and natural shrines called nemetons. Some Celtic groups also built temples or ritual enclosures. The Celts often made offerings, such as items placed in water, wetlands, or ritual pits and wells. Evidence shows that the Celts sacrificed animals, usually livestock or working animals. Some evidence suggests that humans were also sacrificed, and the Roman writer Caesar claimed that the Gauls burned criminals in a large wicker structure during his accounts of the Gallic Wars.

History

Celtic paganism, as practiced by the ancient Celts, came from Proto-Celtic paganism, which itself was based on Proto-Indo-European paganism. Many gods and goddesses in Celtic stories have similar names or roles in other Indo-European traditions. For example, the Celtic goddess Brigantia is similar to the Roman goddess Aurora, the Vedic goddess Ushas, and the Norse figure Aurvandill. The Welsh goddess Arianrhod is similar to the Greek goddess Selene, the Baltic goddess Mėnuo, and the Slavic goddess Myesyats. The Irish goddess Danu is linked to the Hindu goddess Danu and appears in the names of rivers like the Danube, Don, and Dnieper.

After the Roman Empire conquered Gaul (58–51 BCE) and southern Britain (43 CE), Celtic religious practices in those areas changed due to Roman influence. This led to the creation of a mixed religion called Gallo-Roman paganism, which included gods like Lenus Mars, Apollo Grannus, and Telesphorus.

The Gauls slowly converted to Christianity starting in the third century. After the Roman Empire left Britain around 410 CE, Celtic paganism in much of what became England was replaced by Anglo-Saxon paganism. In Britain and Ireland, Celtic people gradually turned to Christianity from the fifth century onward. However, Celtic paganism influenced later cultures, shaped mythology, and in the 20th century inspired a modern religious movement called Celtic neopaganism.

Some characters from medieval Irish myths are thought to be based on older gods. According to Miranda Aldhouse-Green, the Celts also believed in animism, meaning they thought every part of nature had a spirit.

Today, many Neopagan groups claim to be connected to Celtic paganism. These groups include Reconstructionists, who try to follow ancient Celtic religious practices as closely as possible, and New Age groups that use Celtic myths and symbols for inspiration. One well-known example is Neo-Druidry.

Deities

Celtic religion was polytheistic, meaning it believed in many gods and goddesses. Some deities were worshiped only in small areas or by specific tribes, while others were honored across larger regions. Over 200 names of Celtic gods and goddesses have been recorded, though many may have been different names or titles for the same deity.

Many Celtic groups seemed to worship a father god, often associated with the tribe and the dead (Toutatis was one name for him), and a mother goddess linked to the land, fertility, and earth (Matrona was one name for her). The mother goddess could also appear as a war goddess, protecting her people and their land, such as Andraste. A male god connected to the sky, thunder, and the bull was likely Taranis. Other gods included Lugus, a god of skills and crafts, and Gobannos, a god of metalwork. Healing gods, like Sirona and Borvo, were often linked to sacred springs. Other widely worshiped deities included Cernunnos, a horned god; Epona, a goddess of horses and fertility; Maponos, a divine son; and Belenos, Ogmios, and Sucellos. Some deities were considered threefold, such as the Three Mothers.

Some Greco-Roman writers, like Julius Caesar, did not record the original Celtic names of gods but instead compared them to Roman or Greek gods. Caesar claimed the most widely worshiped Gaulish god was Mercury, the Roman god of trade, and that the Gauls also honored Apollo, Minerva, Mars, and Jupiter. He noted that the Gauls believed all people descended from a god of the underworld, whom he compared to Dīs Pater.

Other classical sources suggest the Celts worshiped natural forces and did not imagine gods as human-like figures.

In medieval Irish and Welsh texts, human-like mythological characters appeared, which some scholars believe were inspired by earlier gods. However, historian Ronald Hutton warned against assuming all such figures were once gods. He explained that while some characters, like Medb or St. Brigit, may have once been seen as divine, others, such as warriors in stories, were similar to figures in Greek myths, existing between humans and gods. Hutton compared this to seeing characters like Cú Chulainn or Fergus Mac Roich as humans, not former gods.

Scholar Barry Cunliffe noted that Irish myths show a contrast between male tribal gods and female land goddesses. Anne Ross observed that Celtic gods were often described as wise, skilled in storytelling, craftsmanship, healing, and warfare—qualities admired by Celtic people.

Insular Celts (those living on islands like Britain and Ireland) made oaths by swearing to their tribal gods and the land, sea, and sky. For example, they might say, "I swear by the gods by whom my people swear," and "If I break my oath, may the land open to swallow me, the sea rise to drown me, and the sky fall upon me." This was an example of the Celtic concept of "threefold death," where breaking an oath led to punishment from three natural forces.

Animistic aspects

Some scholars, like Prudence Jones and Nigel Pennick, believe that the Celts honored certain trees. Other scholars, such as Miranda Aldhouse-Green, think that the Celts practiced animism, meaning they believed that spirits lived in all parts of nature and that people could communicate with these spirits.

Places like rocks, streams, mountains, and trees may have had shrines or offerings for local gods. These gods were worshipped only by people who lived near the shrine, not by all Celts as some other gods were. The importance of trees in Celtic religion is shown by the name of the Eburonian tribe, which includes a reference to the yew tree. Also, names like Mac Cuilinn (meaning "son of holly") and Mac Ibar (meaning "son of yew") appear in Irish stories. In Ireland, the salmon, which eats hazelnuts from trees around the well of wisdom (Tobar Segais), was a symbol of wisdom.

Early Celtic art often includes images of animals, especially water birds. These birds may have been important to the Celts because they can move between air, water, and land. Examples of these animal figures include the Torrs Pony-cap and Horns (Scotland), Basse Yutz Flagons (France), Wandsworth Shield (England), and the Dunaverney flesh-hook (late Bronze Age Ireland).

Burial and afterlife

Celtic burial practices, which included placing items like food, weapons, and jewelry with the dead, show that they believed in life after death.

A common idea in later stories from Celtic countries that adopted Christianity was the otherworld. This was a magical place where fairies and other supernatural beings lived. These beings sometimes tried to lure humans into their realm. Some say the otherworld was underground, while others believed it was located far to the west. Some scholars think the otherworld might have been the Celtic afterlife, but there is no clear proof to support this idea.

Celtic practice

Evidence shows that among the Celts, "offerings to the gods were made throughout the landscape – both the natural and the domestic." There were also sacred spaces known by the Gallo-Brittonic word nemeton (plural nemeta), which usually meant a sacred grove or clearing. Greco-Roman accounts describe the Celts worshipping at sacred groves. Tacitus wrote that his men cut down "groves sacred to savage rites." These groves, by their nature, would not survive in the archaeological record, so there is no direct evidence for them today. Certain springs were also considered sacred and used for worship in the Celtic world. Notable examples include the sanctuary of Sequana at the source of the Seine in Burgundy and Chamalieres near Clermont-Ferrand. At these sites, many votive offerings have been found, mostly wooden carvings, though some are decorated with metal.

During the Iron Age, the Celtic peoples of Gaul, Belgica, and Britain built temples made of square or circular wooden buildings, often placed inside rectangular enclosures. In southern Germany, people built rectangular ditched enclosures called viereckschanzen; in some cases, these were sacred spaces where votive offerings were buried in deep pits. In Ireland, religious buildings and enclosures were circular. Barry Cunliffe noted that "the size and grandeur of Irish religious sites make them different from their British and European counterparts," with examples like the Hill of Tara (Temair) and Navan Fort (Emain Macha).

When the Roman Empire conquered Celtic lands, earlier sacred sites were often reused, and Roman temples were built on them. Romano-Celtic temples (fanum) are found only in the northwestern Celtic regions of the empire. They differ from classical Roman temples, and their designs are thought to be heavily influenced by earlier Celtic wooden temples.

The Celts made votive offerings to their gods, which were buried in the earth, thrown into rivers, or placed in bogs. Barry Cunliffe explained that deposits were often placed in the same locations repeatedly, showing continued use "over time, perhaps seasonally or when specific events required a response."

There was a trend to offer items related to warfare in watery areas. Evidence of this is found not only in Celtic regions but also in Late Bronze Age societies and in places like Denmark. For example, the river Thames in southern England had items like the Battersea Shield, Wandsworth Shield, and Waterloo Helmet deposited in it. These items were valuable and required much effort to make. Another example is Llyn Cerrig Bach in Anglesey, Wales, where battle-related offerings were thrown into a lake from a rocky outcrop around the late first century BC or early first century AD.

At times, jewelry and other high-value items not related to warfare were also placed in ritual contexts. At Niederzier in the Rhineland, a post believed to have religious significance had a bowl nearby containing forty-five gold coins, two torcs, and an armlet. Similar deposits have been found elsewhere in Celtic Europe.

There is evidence that ancient Celts sacrificed animals, usually livestock or working animals. The idea was that giving life to the Otherworld pleased the gods and created a connection between the worlds. Animal sacrifices could be acts of thanks, to ask for health or fertility, or for divination. Some animals were fully given to the gods (by burying or burning), while others were shared between gods and humans (part eaten, part set aside).

Pliny the Elder, a Roman writer and military commander in the 1st century AD, wrote that druids performed a ritual in which two white bulls were sacrificed, mistletoe was cut from a sacred oak with a golden sickle, and an elixir was made from it to cure infertility and poison.

Archaeologists found that at some Gaulish and British sanctuaries, horses and cattle were killed and their bodies carefully buried. At Gournay-sur-Aronde, the animals were left to decompose before their bones were buried around the sanctuary’s boundaries along with broken weapons. This happened every ten years or so. An avenue of animal burial pits led to a sacred building at Cadbury. In southern Britain, some tribes buried horses and dogs in grain storage pits, likely as thanksgiving sacrifices to underworld gods when the grain was no longer useful.

Irish mythology describes the tarbfeis (bull feast), a ritual in which a bull was sacrificed, and a seer slept in the bull’s hide to see visions of the future king.

After the 12th-century Norman invasion of Ireland, Gerald of Wales wrote in Topographia Hibernica that Irish kings of Tyrconnell were inaugurated with a horse sacrifice. He described a white mare being cooked into a broth, which the king bathed in and drank. This was seen as propaganda to portray the Irish as barbaric, though similar horse sacrifices linked to kingship are mentioned in Scandinavia and India (see ashvamedha).

There is some evidence that ancient Celts practiced human sacrifice. Roman and Greek sources describe the Gauls burning animal and human sacrifices in a large wicker figure, the wicker man, with human victims often being criminals. Posidonius wrote that druids predicted the future by observing the death throes of victims. Caesar also wrote that slaves of Gaulish chiefs were burned with their master’s body during funerals. In the 1st century AD, Lucan mentioned human sacrifices to the gods Esus, Toutatis, and Taranis. A 4th-century commentary on Lucan stated that sacrifices to Esus involved hanging, to Toutatis involved drowning, and to Taranis involved burning. Cassius Dio wrote that Boudica’s forces impaled Roman captives during her rebellion, with sacrifices in sacred groves. Historians caution that these accounts may have been biased to make the Celts seem barbaric.

Some archaeological evidence suggests human sacrifice among Celts, though it is rare. Ritual beheading and headhunting were major practices, supported by findings like skulls in Londinium’s River Walbrook and headless bodies at Gournay-sur-Aronde.

Several ancient Irish bog bodies have been interpreted as kings ritually killed, possibly after disasters like crop failures. Some were placed in bogs on territorial boundaries or near royal sites, and some had a ceremonial last meal.

The image of the human head is believed by many archaeologists and historians to have played an important role in Celtic religion.

Priesthood

According to several Greco-Roman writers, including Julius Caesar, Cicero, Tacitus, and Pliny the Elder, the societies of Gaul and Britain respected a group of spiritual and religious leaders called the druids. Their roles varied slightly in different accounts, but Caesar’s description, considered the most detailed and earliest original text, stated that druids were responsible for religious practices, such as performing sacrifices and interpreting rituals. He also claimed they conducted human sacrifices, like burning people inside wicker figures. However, some historians have questioned the accuracy of these accounts, suggesting they may be biased. In Irish sources, druids were also described as priests with supernatural abilities, using magic for divination and cursing, and they opposed the spread of Christianity.

Historians and archaeologists have offered different interpretations of the druids. Peter Berresford Ellis compared them to the Indian Brahmin caste, while Anne Ross viewed them as tribal priests similar to shamans. Ronald Hutton was skeptical, arguing that the evidence about druids is unreliable, making it difficult to know much about them with certainty, even though they likely existed.

In Ireland, the filid were poets who preserved stories, composed poetry, and memorized long poems. They were also considered magicians, as Irish magic was closely linked to poetry. A poet’s satire could be a serious curse. In Ireland, a "bard" was a lower-ranking poet, more of a singer who recited poems, rather than a poet with magical abilities. In Welsh tradition, the term "bardd" was used for poets.

Celtic poets, regardless of rank, created eulogies and satires. Their main duty was to write and recite poems about heroes and their achievements, and to memorize the family histories of their patrons. Their success depended on raising their patrons’ fame through stories, poems, and songs. In the 1st century AD, the Roman writer Lucan referred to "bards" as the poets and musicians of Gaul and Britain. Over time, the bardic tradition faded in Roman Gaul but remained in Ireland and Wales until the Middle Ages. In Wales, the bardic order was later revived and organized by Iolo Morganwg, a poet and forger. This tradition continues today, centered around events called eisteddfods in Welsh literary communities.

Calendar

The oldest known Celtic calendar is called the Coligny calendar. It was created in the 2nd century, which places it firmly in the Gallo-Roman period, a time when Roman and Celtic cultures interacted.

Some feast days in the medieval Irish calendar have been suggested to have roots in older, prehistoric festivals, especially when compared to terms in the Coligny calendar. It is unclear what religious festivals the ancient Celts celebrated. However, the Insular Celtic peoples observed four seasonal festivals, which the medieval Gaels named Beltaine (May 1), Lughnasadh (August 1), Samhain (November 1), and Imbolc (February 1). Beltaine is specifically described by medieval Irish writers as having ancient origins. The festivals of Samhain and Imbolc are not linked to "paganism" or druidry in Irish legends. Nevertheless, since the 19th century, some scholars, including John Rhys and James Frazer, have suggested that Samhain may have marked the "Celtic new year."

Gallo-Roman religion

Gallo-Roman religion was a combined belief system that developed in Roman Gaul when local Celtic traditions merged with Roman and Greek religious practices. This blending happened as people chose to adopt some Roman customs while keeping parts of their own culture. Native gods were often paired with Roman gods, such as Lenus Mars and Sulis Minerva, and some Celtic figures, like Epona, were included in Roman worship. Religious structures, like the Jupiter Column, and the creation of paired deities showed how Roman and Celtic traditions came together. Practices such as walking around sacred spaces (circumambulation) and the importance of water near temples reflected the lasting influence of Celtic beliefs.

Roman leaders, such as Augustus and Tiberius, stopped the traditional Celtic religious leaders called druids from having power. They replaced them with Roman-style priests and used Latin in religious ceremonies. However, local religious traditions continued in ways like the worship of Cernunnos and the way Roman gods were shown in local art.

Offerings made by people, healing temples, and changes to religious buildings showed how Roman and Celtic cultures mixed. Even though some practices, like headhunting or human sacrifices, were banned, they may have continued or changed under Roman rule.

Christianization

Celtic societies living under Roman rule likely became Christian in a way similar to other parts of the Roman Empire. There is very little information in Christian writings about the specific religious practices of the Celtic people or their experiences in the Empire. Saint Paul’s letter to the Galatians may have been written for a group of people that included individuals of Celtic background.

In Ireland, the main Celtic region never conquered by the Romans, the shift to Christianity had a major impact on society and religion starting in the 5th century. However, details about this change are mostly guessed based on writings from much later times. By the early 700s, the church had reduced the influence of Irish druids, who were religious leaders before Christianity. Meanwhile, the filidh, who were experts in traditional knowledge, worked well with church leaders and kept many of their old customs, status, and rights. Most of the ancient Irish stories and writings that survived were recorded in monastery scriptoria, or writing rooms. Today, scholars study these texts to understand how much of the old traditions remained and how much changed with the church.

Cormac’s Glossary, written around 900 AD, says that Saint Patrick stopped certain rituals of the filidh that involved offerings to "demons." The church also worked to stop practices like animal sacrifices that went against Christian beliefs. Many old rituals that remained were connected to filidhecht, the traditional skills of the filidh, or to the idea of sacred kingship. One example is the belief in the sacred marriage of a king and the goddess of sovereignty, called "banais ríghi." This ritual, which was central to a king’s coronation, was likely removed by the church early on, but the idea of this union stayed in stories for many centuries.

Modern scholars explain that the term "Celtic Church" is misleading. It suggests a separate church, but in reality, the churches in Ireland and Britain were part of the larger Latin Christian world. They had some unique traditions, like a special way to calculate Easter, a different style of cutting hair for monks, and the idea of traveling to spread Christianity. These differences did not create a major religious split but showed how local traditions shaped church practices.

Folkloristic survivals

Nagy observed that the Gaelic oral tradition has remained very consistent over time. The fact that stories were told in the 19th century in nearly the same way as they appear in ancient manuscripts suggests that much of what monks recorded was likely much older. While some tales include Christian additions that are clearly visible, many of these additions seem to be added later as notes to the main parts of the stories, which probably reflect traditions even older than the manuscripts themselves.

Mythology based on (but not exactly the same as) pre-Christian traditions was still widely known in Celtic-speaking cultures in the 19th century. During the Celtic Revival, these traditions were collected and edited, turning them into a literary tradition that later influenced modern ideas about "Celticity." Several Celtic celebrations have been practiced in some form since ancient times, such as the Beltane festival and the Killorglin Puck Fair, which appears to be a survival of the Lughnasadh festival.

Various rituals involving visits to places like hills and sacred wells believed to have healing or beneficial powers are still performed today. These include traditions such as clootie wells in Scotland, Ireland, and Cornwall, and the practice of well dressing in the English Midlands. This is also true for wish trees, which are part of the clootie well tradition. Evidence from the European continent shows that many figures still known in folklore in Celtic countries today, or those involved in post-Christian mythology, were also worshipped in areas that had no written records before Christianity. On the Inishkea Islands off the west coast of Ireland, Celtic pagan rituals were apparently practiced well into the nineteenth century.

Other possible traces of Celtic paganism include the Irish strawboy tradition and Wren Day traditions, as well as the Shetlandic practice of Skekling, all of which involve wearing unusual costumes made of straw.

In Twilight of the Celtic Gods (1996), Clarke and Roberts describe several very traditional folkloristic customs in remote rural areas of Great Britain, such as the Peak District and Yorkshire Dales. These include claims that pre-Christian Celtic traditions of honoring stones, trees, and bodies of water still survive in those regions.