Ancient Celtic religion, also called Celtic paganism, was the belief system of the Celtic people who lived in Europe long ago. Since there are no written records from the Celts themselves, information about their religion comes from archaeology, writings by Greek and Roman people (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 specific gods worshipped changed over time and in different areas, there were general similarities among the Celts in their beliefs and practices. Some widely worshipped gods include Lugus, Toutatis, Taranis, Cernunnos, Epona, Maponos, Belenos, and Sucellos. Sacred springs were often linked to gods associated with healing. A common idea in Celtic religion was triplicity, meaning some gods were seen as having three parts, such as the Three Mothers.

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

History

Celtic paganism, as practiced by the ancient Celts, came from Proto-Celtic paganism, which itself came from Proto-Indo-European paganism. Many gods in Celtic stories have similar names to gods 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 similar 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 religion in those areas changed because of Roman influence. This led to a mixed religion called Gallo-Roman religion, which included gods like Lenus Mars, Apollo Grannus, and Telesphorus.

The Gauls slowly converted to Christianity starting in the third century. After the Roman rule in Britain ended around 410 CE, Celtic paganism was gradually replaced by Anglo-Saxon paganism in much of what became England. In Britain and Ireland, Celtic people slowly converted to Christianity from the fifth century onward. However, Celtic paganism had a lasting influence on many Celtic nations, shaped their myths, and in the 20th century inspired a new religious movement called Celtic neopaganism.

Some characters from medieval Irish stories 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 accurately as possible, and New Age groups that take inspiration from Celtic myths and symbols. One well-known example is Neo-Druidry.

Deities

Celtic religion was polytheistic, meaning it believed in many gods and goddesses. Some deities were worshipped only in small areas or by specific tribes, while others were worshipped by people 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.

The various Celtic groups often had a father god, who was sometimes seen as the protector of the tribe and the dead (one name for him was Toutatis). They also had a mother goddess connected to the land, fertility, and earth (one name for her was Matrona). This goddess could also appear as a war protector, such as Andraste. There was also a male god linked to the sky and thunder, known as 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 tied to sacred springs. Other widely worshipped deities included Cernunnos, the horned god; Epona, a goddess of horses and fertility; Maponos, a divine son; and Belenos, Ogmios, and Sucellos. Some deities were seen as threefold, such as the Three Mothers.

Greco-Roman writers, like Julius Caesar, did not always record the original Celtic names of the gods. Instead, they compared them to Roman or Greek gods. Caesar wrote that the most widely worshipped Gaulish god was Mercury, the Roman god of trade, and that the Gauls also worshipped 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 stated that the Celts worshipped natural forces and did not imagine their gods as human-like.

In medieval Irish and Welsh texts, many human-like mythological figures appeared. Scholars have suggested some of these characters may have originally been gods. However, Ronald Hutton warned that not all figures in these stories were once considered gods. Some, like Medb or St. Brigit, may have been divine, but others, such as warriors like Cú Chulainn or Fergus Mac Roich, were more like humans in stories, similar to figures in Greek myths.

Barry Cunliffe believed Irish myths showed a contrast between male gods linked to tribes and female goddesses connected to the land. Anne Ross noted that the gods were often described as wise, skilled in crafts, storytelling, and healing, reflecting qualities admired by the Celts.

Insular Celts (those living on islands) swore oaths by their tribal gods and natural elements like the land, sea, and sky. For example, they might say, "I swear by the gods my people worship" or "If I break my oath, may the land swallow me, the sea drown me, and the sky fall on me." This type of oath was called the Celtic Threefold death.

Animistic aspects

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

Places like rocks, streams, mountains, and trees might have had shrines or gifts left for a god who lived there. These gods were local, worshipped only by people near the shrine, not gods that all Celts shared. Trees were important in Celtic religion, as shown by the name of the Eburonian tribe, which includes a word for the yew tree. Names like Mac Cuilinn (son of holly) and Mac Ibar (son of yew) also appear in Irish stories. In Ireland, the salmon that eats hazelnuts from trees around the well of wisdom (Tobar Segais) was a symbol of knowledge.

Early Celtic art often shows animals, especially water birds. These birds could move on air, water, and land, which may have made them special to the Celts. Examples of these artworks 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 people buried food, weapons, and jewelry with the dead. This shows they believed in life after death. In stories from Celtic countries that later became Christian, a common idea was the "otherworld." This was a place where fairies and other magical creatures lived. They sometimes tried to lure humans there. Some people thought the otherworld was underground. Others believed it was far to the west. Some experts think the otherworld was where Celts believed people went after death. However, there is no clear proof of this.

Celtic practice

Evidence shows that the Celts made offerings to their gods across the land, including natural areas and homes. Sacred spaces, called "nemeton" in the Gallo-Brittonic language, were often groves or open areas in forests. Greco-Roman writers, like Tacitus, described how Celts worshipped in these groves. However, because these groves were natural, they rarely left clear signs for archaeologists to find today. Some springs were also considered sacred and used for worship. In Gaul, for example, the sanctuary of Sequana near the Seine and Chamalieres near Clermont-Ferrand had many wooden carvings and metal items found as offerings.

During the Iron Age, Celts in Gaul, Belgica, and Britain built temples made of wood, often inside rectangular enclosures. In southern Germany, they created rectangular ditched enclosures called viereckschanzen, where offerings were sometimes buried in deep pits. In Ireland, religious sites were usually circular. Barry Cunliffe noted that Irish religious places, like the Hill of Tara and Navan Fort, were more grand than those in Britain or Europe.

When the Roman Empire conquered Celtic lands, many older sacred sites were reused, and Roman temples were built on them. Romano-Celtic temples, called "fanum" in Latin, were found mainly in northwestern Celtic regions. These temples were different from Roman ones and likely influenced by earlier Celtic wooden temples.

The Celts gave gifts to their gods by burying them in the ground, throwing them into rivers, or placing them in bogs. Barry Cunliffe explained that these offerings were often placed in the same spots repeatedly, suggesting they were used regularly, possibly for seasonal events or important occasions.

There was a trend to leave items related to war in water, such as the Battersea Shield, Wandsworth Shield, and Waterloo Helmet found in the Thames. Similar items were also found in Denmark, showing this practice existed before the Celts. In Wales, offerings like weapons were thrown into Llyn Cerrig Bach around the time of the first century BC or AD.

At times, non-war items like jewelry were also used in rituals. In Niederzier, a religious site had a bowl with gold coins, torcs, and an armlet buried nearby.

There is evidence that the Celts sacrificed animals, usually livestock or working animals. This was believed to please the gods and create a connection between the human and spirit worlds. Sacrifices could be for thanks, to ask for health, or for divination. Some animals were fully given to the gods (by burning or burying), while others were shared between gods and humans.

Pliny the Elder, a Roman writer, described druids cutting mistletoe from a sacred oak with a golden sickle to make medicine. At sites like Gournay-sur-Aronde and Cadbury, animals were killed and buried near temples. In Britain, horses and dogs were sometimes buried in grain storage pits as thanksgiving to underworld gods.

Irish myths mention the tarbfeis, a ritual where a bull was sacrificed, and a seer slept in its hide to see the future. After the Norman invasion of Ireland, Gerald of Wales wrote that Irish kings were inaugurated with a horse sacrifice, though this may have been propaganda. Similar practices were recorded in Scandinavia and India.

Some evidence suggests the Celts practiced human sacrifice. Roman and Greek writers, like Julius Caesar and Strabo, described burning people and animals in large wicker figures, with criminals as victims. Others, like Posidonius, wrote that druids used the death throes of victims to predict the future. Caesar also mentioned slaves being burned with their masters’ bodies. Roman writers like Lucan and Cassius Dio described sacrifices to gods like Esus, Toutatis, and Taranis, with different methods for each. However, historians caution that these accounts may have exaggerated Celtic cruelty.

Archaeological evidence supports some human sacrifices, though they were rare. Ritual beheading and headhunting were common, as seen in skulls found in Londinium’s River Walbrook and headless bodies at Gournay-sur-Aronde. In Ireland, some bog bodies were found near royal sites or borders, possibly kings sacrificed during disasters. These individuals often had ceremonial meals before death.

Many scholars believe the human head held special religious meaning in Celtic culture.

Priesthood

According to ancient Roman and Greek writers like Julius Caesar, Cicero, Tacitus, and Pliny the Elder, people in Gaul and Britain respected a group of magico-religious specialists called the druids. These writers described the druids in different ways, but Caesar’s account, considered the most detailed and earliest original text, said they performed religious duties, such as leading sacrifices and interpreting rituals. He also claimed they oversaw human sacrifices, like burning people inside large wicker figures. However, some historians argue these descriptions may be biased or incorrect. In Ireland, local sources called the druids priests and sorcerers who used magic for divination and curses, and who resisted the spread of Christianity.

Many historians and archaeologists have different views about the druids. Peter Berresford Ellis thought they were similar to the Indian Brahmin caste, while Anne Ross believed they were more like tribal priests, similar to shamans. Ronald Hutton doubted many claims about the druids, saying the evidence is unclear and that "we can know almost nothing for sure about ancient druids, even though they existed and are more like legendary figures than real people."

In Ireland, the filid were poets who memorized and shared stories, poems, and knowledge. They were also seen as magicians because Irish magic was closely tied to poetry. A poet’s satire could harm someone they criticized. In Ireland, a "bard" was a less skilled poet, more like a singer who repeated songs, while a fili was a highly respected poet with magical abilities. In Wales, the poet was always called a "bardd."

Celtic poets, regardless of their rank, wrote poems praising heroes and criticizing people. They also remembered the family histories of important people. Their success depended on making their patrons famous through stories, poems, and songs. In the first century AD, the Roman writer Lucan called "bards" the poets and singers of Gaul and Britain. Over time, this tradition faded in Roman Gaul but lasted in Ireland and Wales until the Middle Ages. In Wales, the bardic tradition was later revived and organized by a poet named Iolo Morganwg. This tradition continues today through events called eisteddfods, which are held at all levels of Welsh literary culture.

Calendar

The oldest known Celtic calendar is the Coligny calendar, which dates back to the 2nd century and is from the Gallo-Roman period.

Some days in the medieval Irish calendar have sometimes been thought to have origins in older festivals, especially when compared to terms in the Coligny calendar. It is unclear what religious festivals the ancient Celts celebrated, but the Insular Celtic peoples observed four seasonal festivals. These were called Beltaine (1 May), Lughnasadh (1 August), Samhain (1 November), and Imbolc (1 February) by medieval Gaels. Beltaine is said to have an ancient origin by medieval Irish writers. The festivals of Samhain and Imbolc are not connected to "paganism" or druidry in Irish legends. However, 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 certain aspects of Roman culture while keeping parts of their own. For example, native gods like Lenus Mars and Sulis Minerva were paired with Roman gods, and the Celtic figure Epona was included in Roman worship. Religious structures such as the Jupiter Column and the creation of paired deities showed how Roman and Celtic traditions came together. Practices like walking around sacred spaces and placing temples near water reflected the lasting influence of Celtic customs.

Roman leaders, such as Augustus and Tiberius, stopped the traditional roles of druid groups and replaced them with Roman-style religious leaders and Latin prayers. However, local religious traditions remained, such as the continued worship of Cernunnos and the way Roman gods were shown in local artwork. Offerings made for protection, healing temples, and changes to sacred buildings showed how cultures mixed. Even though some practices, like headhunting and possibly human sacrifices, were banned, they may have continued or changed under Roman rule.

Christianization

Celtic societies living under Roman rule probably became Christian in a way similar to the rest of the Roman Empire. Very little information about the religious practices of the Celtic people in the Empire is found in Christian writings. Saint Paul’s letter to the Galatians may have been written for a group that included people of Celtic heritage.

In Ireland, the only major Celtic region not conquered by the Romans, the spread of Christianity had a major impact on society and religion starting around the 5th century. However, details about this change are mostly guessed from writings from much later times. By the early 7th century, the church had made druids, who were religious leaders before Christianity, no longer important. Meanwhile, the filidh, who were experts in traditional knowledge, worked well with church leaders and kept many of their old traditions, status, and privileges. Most of the early Irish stories and writings that survived were recorded in monastic centers. Scholars today study these texts to understand how much of the old culture remained and how much was changed by the church.

Cormac’s Glossary, written around 900 AD, says that Saint Patrick stopped certain rituals practiced by the filidh that involved offerings to "demons." The church also tried to stop practices like animal sacrifices that went against Christian beliefs. Many old traditions that survived were connected to filidhecht, the knowledge of the filidh, or to the idea of sacred kingship. An example is the belief in the sacred marriage between a king and a goddess of land and power. This ritual, called the "wedding of kingship," was part of a king’s coronation but was removed by the church early on. However, it continued to appear in stories and writings for many years.

Modern scholars say that the term "Celtic Church" is misleading because it suggests a separate group when, in fact, it was part of the larger Christian world centered in Rome. Churches in Ireland and Britain had some unique practices, such as a special way to calculate the date of Easter, a specific style of cutting hair for monks, and the idea of traveling far to spread Christianity. These differences did not mean the churches were in conflict with others, but they were distinct from practices in other parts of Europe.

Folkloristic survivals

Nagy has observed that the Gaelic oral tradition has remained largely unchanged over time. Tales told in the 19th century are very similar to those written in ancient manuscripts, suggesting that many of the stories recorded by monks were much older. While some stories include Christian additions, these often seem like later additions rather than central parts of the tales. These main parts likely reflect traditions that existed long before the manuscripts were written.

Myths based on older, pre-Christian traditions were still widely known in Celtic-speaking cultures during the 19th century. During the Celtic Revival, these old traditions were collected and written down, becoming part of a literary tradition. This helped shape modern ideas about Celtic culture. Some festivals, like Beltane and the Killorglin Puck Fair (a possible remnant of Lughnasadh), have been celebrated in some form since ancient times.

Rituals involving visits to places like hills and sacred wells, believed to have healing or helpful powers, are still practiced today. Examples include clootie wells in Scotland, Ireland, and Cornwall, and well dressing in the English Midlands. Similar traditions include wish trees, which are linked to clootie wells. Evidence from Europe suggests that some figures in folklore and post-Christian mythology were once worshipped in areas without written records before Christianity. On the Inishkea Islands near Ireland’s west coast, Celtic pagan rituals were practiced into the 19th century.

Other possible traces of Celtic paganism include the Irish strawboy tradition, Wren Day customs, and the Shetlandic practice of Skekling, all involving unusual straw costumes. In Twilight of the Celtic Gods (1996), Clarke and Roberts describe conservative folklore traditions in remote areas of Great Britain, such as the Peak District and Yorkshire Dales. These include claims of surviving pre-Christian traditions, such as the worship of stones, trees, and bodies of water.