The Celts were a group of people in Europe and Anatolia who shared similar languages and cultures. Major Celtic groups included the Gauls, the Celtiberians and Gallaeci in Iberia, the Britons, Picts, and Gaels in Britain and Ireland, the Boii, and the Galatians. Scholars debate how to define the Celts, as the connection between their language, culture, and ethnicity is not fully understood. Today, the term "Celt" most often refers to people who spoke Celtic languages rather than to a single ethnic group.

The origins of the Celts are debated. One traditional theory, called "Celtic from the East," suggests that the proto-Celtic language began in the late Bronze Age Urnfield culture of central Europe, which was named after burial sites in southern Germany. This theory links the Celts to the Iron Age Hallstatt culture in Austria and the La Tène culture in Switzerland, which followed the Urnfield culture. It claims that Celtic culture spread westward and southward through migration or diffusion. Other newer theories, such as "Celtic from the West" and "Celtic from the Centre," propose different origins for the proto-Celtic language, including the Atlantic Bronze Age coastal zone or Bronze Age Gaul. By the 3rd century BC, Celtic culture had reached as far east as central Anatolia in Turkey.

The earliest confirmed examples of Celtic language are the Lepontic inscriptions from the 6th century BC. Continental Celtic languages are mostly known from inscriptions and place names. Insular Celtic languages, spoken on islands like Britain and Ireland, are recorded from the 4th century AD in Ogham inscriptions, though they were spoken earlier. The Celtic literary tradition began with Old Irish texts around the 8th century AD. Celtic myths and stories were recorded in early Irish and Welsh writings. Much of what is known about early Celts comes from Greco-Roman writers, who often described them as barbarian tribes. The Celts practiced an ancient religion guided by druids.

The Celts frequently clashed with the Romans, as seen in conflicts like the Roman–Gallic Wars, the Celtiberian Wars, and the Roman conquests of Gaul and Britain. By the 1st century AD, most Celtic territories were part of the Roman Empire. By around 500 AD, due to Roman influence and the movement of Germanic tribes, Celtic culture was mostly limited to Ireland, western and northern Britain, and Brittany. Between the 5th and 8th centuries, Celtic-speaking communities in these regions developed a shared cultural identity through common language, religion, and art.

Over time, Insular Celtic culture split into the Gaels (including Irish, Scots, and Manx speakers) and the Celtic Britons (including Welsh, Cornish, and Bretons). A modern Celtic identity was created during the Romanticist Celtic Revival in the 18th and 19th centuries. Today, Irish, Scottish Gaelic, Welsh, and Breton are still spoken in parts of their historical regions, while Cornish and Manx are being revived.

Names and terminology

The first time the name "Celts" was written was by a Greek geographer named Hecataeus of Miletus in 517 BC. He used the Greek word "Keltoi" to describe people living near Massilia, which is now Marseille in southern Gaul. In the fifth century BC, another Greek writer named Herodotus wrote about people called "Keltoi" living near the source of the Danube River and in the far west of Europe. The meaning of "Keltoi" is not clear. Some experts think it comes from an ancient language word meaning "to hide" or "to heat." Others suggest it might be related to the word "kel" in Old Irish and Welsh, which means "to push forward." It could also come from the early Celtic word "kel-o-." The name "Celt" appears in the names of some ancient Gauls, such as Celtillus, who was the father of Vercingetorix. A scholar named McCone (2006) believed the name might mean "the people or descendants of the hidden one," linking it to a Gaulish god called Dis Pater and the Germanic word "Hel." Others think the Greeks created the name. A linguist named Patrizia de Bernardo Stempel suggested it might mean "the tall ones."

In the first century BC, a Roman leader named Julius Caesar wrote that the Gauls called themselves "Celts" in their own language, which was Latin: "Celtae." This shows that even if others gave them the name, the Celts used it themselves. A Greek geographer named Strabo, writing near the end of the first century BC, described the people of Gaul as "Gallic" or "Galatic," and also called the region "Celtica." He also wrote about Celtic people in Iberia, calling them "Celtiberi" and "Celtici." A Roman writer named Pliny the Elder noted that the word "Celtici" was used as a tribal name in Lusitania, which has been confirmed by written records found on stones.

A Latin name for the Gauls was "Galli," which might come from a Celtic word meaning "power" or "strength." The Greek name "Galatai" (Latinized as "Galatae") likely has the same origin, referring to the Gauls who settled in a region called Galatia. The ending "-atai" might be a Greek addition. A linguist named Kim McCone suggested the name "Galatai" came from the Celtic word "galatis," meaning "fierce" or "angry," and was used to describe young warrior groups. He explained that the Greeks might have used this name because they often saw fierce young warriors from the Gauls.

Some scholars do not use the word "Celt" to describe the people of Britain and Ireland during the Iron Age because ancient writers did not call them "Keltoi" or "Celtae." However, these people spoke Celtic languages, shared other cultural traits, and a Roman historian named Tacitus said the Britons had customs and religions similar to the Gauls.

For at least 1,000 years, no one used the word "Celt" to describe themselves. People began using it again around 1700 after finding references to "Celtic" in old texts. The word "Celtic" was then used to describe the culture, history, traditions, and language of modern Celtic nations, including Ireland, Scotland, Wales, Cornwall, Brittany, and the Isle of Man. The word "Celt" is a modern English term first used in 1707 by a scholar named Edward Lhuyd. His work, along with others, helped scholars study the languages and history of early Celtic people in Great Britain. The English words "Gaul," "Gauls," and "Gaulish" come from French words borrowed from the Frankish language, which meant "Roman land." This is related to the Proto-Germanic word "walha," meaning "foreigner" or "Celt." The word "Welsh" in English comes from the same root.

The word "Celtic" refers to a group of languages and, more generally, means "of the Celts" or "in the style of the Celts." Several ancient cultures are considered Celtic because of the unique tools and objects they used. Inscriptions on these objects help connect languages to artifacts. Today, the idea of a Celtic cultural identity focuses on similarities in languages, art, and ancient texts, as well as sometimes shared traditions, social structures, and myths. Earlier ideas suggested these similarities meant the Celts had a common "racial" origin, but modern theories say they reflect shared cultural and linguistic heritage rather than genetics. Celtic cultures were diverse, but they all used a Celtic language.

Today, the term "Celtic" refers to the languages and cultures of Ireland, Scotland, Wales, Cornwall, the Isle of Man, and Brittany. These are the regions where Celtic languages are still spoken. The main languages are Irish, Scottish Gaelic, Welsh, and Breton, with Cornish and Manx being revived in recent years. Some people also try to restore Cumbric, a Celtic language once spoken in northern Britain. In mainland Europe, people in areas like western Iberia (Portugal and parts of Spain) claim a Celtic heritage, even though no Celtic languages are spoken there now.

People who lived in mainland Europe and spoke Celtic languages are called "Continental Celts." Those who lived on the British and Irish islands and spoke Celtic languages are called "Insular Celts." The people of Brittany speak a language that came from Insular

Origins

The Celtic languages are part of the larger Indo-European language family. By around 400 BC, when written records first mention the Celts, they were already divided into several language groups and lived in many areas of western Europe, including the Iberian Peninsula, Ireland, Britain, and parts of mainland Europe. These languages later developed into groups such as Celtiberian, Goidelic, and Brittonic.

Most scholars in the 20th century believed that the Celts and the early Celtic language originated from the Urnfield culture in central Europe around 1000 BC. Over the next few hundred years, this culture spread westward and southward. The Urnfield culture was most active in central Europe during the late Bronze Age, from about 1200 BC to 700 BC. The spread of iron-working led to the Hallstatt culture (800 to 500 BC), which developed from the Urnfield culture in areas north of the Alps. The Hallstatt culture later became the La Tène culture, which began around 450 BC and is closely linked to Celtic art.

In 1846, Johann Georg Ramsauer discovered an ancient burial site with unique grave goods in Hallstatt, Austria. He believed these graves were Celtic because they dated to the time when the Celts were mentioned near the Danube River by the ancient writer Herodotus. Similar sites and artifacts were found across Europe and were named the "Hallstatt culture." In 1857, an archaeological site called La Tène was found in Switzerland. The artifacts from this site had a unique style, and similar items were found in areas where Celts lived. By the 1870s, scholars began to associate these artifacts with the Celts. However, the Roman Empire later conquered this region, and the La Tène style was still visible in some Gallo-Roman artifacts. In Britain and Ireland, the La Tène style survived and later appeared in Insular art.

The theory that the Urnfield and Hallstatt cultures were the origins of the Celts was challenged in the late 20th century. This happened when older Celtic-language inscriptions were found in northern Italy (Lepontic) and Iberia (Celtiberian), dating to the 6th and 2nd centuries BC. These regions were not part of the Hallstatt or La Tène cultures at the time. Some scholars also questioned the reliance on ancient Greek and Roman writings, such as those by Herodotus, which placed the Celts near the Danube. Research by Stephen Oppenheimer suggested that Herodotus may have believed the Danube originated near the Pyrenees, which aligns with later classical accounts of the Celts living in Gaul and Iberia.

In the late 20th century, new archaeological discoveries led some scholars to reconsider the Urnfield-Hallstatt theory. The term "Celtic" began to refer more to people who spoke Celtic languages rather than to a single culture or ethnic group. A new theory proposed that Celtic languages developed earlier along the Atlantic coast, including Britain, Ireland, Armorica, and Iberia, long before evidence of "Celtic" culture was found in archaeology. Scholars like Myles Dillon and Nora Kershaw Chadwick suggested that the Celtic settlement of the British Isles might date back to the Bell Beaker culture of the Copper and Bronze Age (around 2750 BC). Martín Almagro Gorbea (2001) also proposed that the Celtic language originated in the 3rd millennium BC, with the Bell Beaker culture explaining the spread of Celts across western Europe.

John T. Koch and Barry Cunliffe developed the "Celtic from the West" theory, which suggests that the early Celtic language (Proto-Celtic) arose along the Atlantic coast and was the main language of the Atlantic Bronze Age cultural network. This language later spread inland and eastward. Cunliffe later proposed that Proto-Celtic may have originated in the Atlantic zone as early as 3000 BC and spread eastward with the Bell Beaker culture over the next millennium. His theory is based on the study of ancient place names and the idea that the Tartessian language was Celtic, though many linguists disagree with this.

Celticist Patrick Sims-Williams (2020) explains that "Celt" is now primarily a linguistic term. In his "Celtic from the Centre" theory, he argues that the early Celtic language did not originate in central Europe or the Atlantic but in an area between these regions. He suggests that Proto-Celtic emerged as a distinct Indo-European dialect around the second millennium BC, likely in Gaul (modern France), and then spread in various directions during the first millennium BC. This theory avoids the idea that Celtic was spoken over a large area for a long time without major dialectal changes and aligns with the view that Italic and Celtic languages were connected.

The Proto-Celtic language is usually dated to the Late Bronze Age. The earliest written records of a Celtic language are the Lepontic inscriptions from Cisalpine Gaul (northern Italy), which predate the La Tène period. Other early inscriptions, from the early La Tène period in Massilia (modern Marseille), are in Gaulish, written in the Greek alphabet until the Roman conquest. Celtiberian inscriptions, using the Iberian script, appeared later, after about 200 BC. Evidence of Insular Celtic (spoken in Britain and Ireland) only appears from around 400 AD, in the form of Primitive Irish Ogham inscriptions.

Besides written records, place names (toponymy) are an important source of information about early Celtic languages.

Arnaiz-Villena et al. (2017) found that populations from the Atlantic regions of Europe, such as

Distribution

The Romans called the Celts living in present-day France the Gauls. These people likely lived in areas that included the Low Countries, the Alps, and northern Italy. Julius Caesar described the Gauls who lived in the 1st century BC in his writings called the Gallic Wars.

Eastern Gaul was the center of the western La Tène culture. Later in the Iron Age, Gaul’s social structure became similar to the Romans’, with large towns. Starting in the 3rd century BC, the Gauls began using coins. Some texts written in Greek characters from southern Gaul have survived from the 2nd century BC.

Greek traders founded a city called Massalia around 600 BC. Some items, mostly drinking vessels, were traded up the Rhône River. However, trade was disrupted after 500 BC and shifted over the Alps to the Po Valley in Italy. The Romans arrived in the Rhône Valley in the 2nd century BC and met a population mostly speaking Celtic. Rome wanted better land connections to its Iberian provinces and fought a major battle with the Saluvii at Entremont between 124–123 BC. Over time, Roman control expanded, and the Roman province of Gallia Transalpina formed along the Mediterranean coast. The Romans called the rest of Gaul Gallia Comata, meaning “Long-haired Gaul.”

In 58 BC, the Helvetii planned to move west but Julius Caesar forced them to return. He then fought against various tribes in Gaul and by 55 BC had taken control of most of the region. In 52 BC, Vercingetorix led a rebellion against Roman rule but was defeated at the Battle of Alesia and surrendered.

After the Gallic Wars (58–51 BC), Caesar’s Celtica became the main part of Roman Gaul, forming the province of Gallia Lugdunensis. This area was bounded by the Garonne River to the south and the Seine and Marne Rivers to the north. The Romans added parts of this region to neighboring provinces, Belgica and Aquitania, especially under Augustus.

Analysis of names and inscriptions suggests that the Gaulish language was spoken across much of what is now France.

Until the late 19th century, scholars believed the Celts were present in the Iberian Peninsula, linked to the Hallstatt and La Tène cultures. However, because Celtic cultures in Iberia were less connected to Central Europe, their presence was not widely recognized. Modern research shows that Celtic influences were strong in what is now Spain and Portugal, especially in central, western, and northern areas.

Roman and Greek sources mention Celts in three parts of the Iberian Peninsula: the eastern Meseta (home to the Celtiberians), the southwest (Celtici in modern-day Alentejo), and the northwest (Gallaecia and Asturias). Recent studies have found several Celtic groups in Spain.

The origins of the Celtiberians may help explain how the Celts spread across the Iberian Peninsula. The Celtic influence in the southwest and northwest was not only due to the Celtiberians. Studies of the Callaici and Bracari in northwest Portugal are helping scholars understand Celtic culture in western Iberia.

John T. Koch of Aberystwyth University suggested that Tartessian inscriptions from the 8th century BC might be Celtic. If true, this would make Tartessian the earliest known Celtic language by over a century.

In Germany, by the late Bronze Age (around 1300–750 BC), the Urnfield culture replaced earlier cultures like the Bell Beaker and Unetice. Meanwhile, the Nordic Bronze Age developed in Scandinavia and northern Germany. The Hallstatt culture, which evolved from the Urnfield, was dominant in Central and Western Europe from the 12th to 8th centuries BC and during the early Iron Age (8th to 6th centuries BC). It was followed by the La Tène culture (5th to 1st centuries BC).

People in central and southern Germany who adopted Hallstatt and La Tène cultural traits were considered Celts. Celtic cultural centers developed in Central Europe during the late Bronze Age (1200–700 BC). Places like the Heuneburg, an important Iron Age city north of the Alps, became key trade hubs connected to the Mediterranean. In the 5th century BC, the Greek historian Herodotus mentioned a Celtic city near the Danube–Pyrene, which scholars believe refers to the Heuneburg. Around 700 BC, Germanic tribes from Scandinavia and northern Germany began moving south, gradually replacing Celts in Central Europe.

The Canegrate culture represented the first wave of proto-Celtic people from the northwest Alps who settled in the western Po Valley between Lake Maggiore and Lake Como (Scamozzina culture). Some evidence suggests proto-Celtic people may have lived in Northwestern Italy as early as the Middle Bronze Age, linked to the Tumulus culture’s bronze production. La Tène cultural items were found across mainland Italy, with the southernmost example being a Celtic helmet from Canosa di Puglia.

Italy is home to Lepontic, the oldest known Celtic language (from the 6th century BC). It was spoken in Switzerland and Northern-Central Italy, from the Alps to Umbria. According to the Recueil des Inscriptions Gauloises, over 760 Gaulish inscriptions have been found in present-day France (except Aquitaine) and Italy, showing the importance of Celtic heritage in the region.

In 391 BC, Diodorus Siculus wrote that Celts from beyond the Alps moved through mountain passes and took control of the area between the Apennine Mountains and the Alps. The Po Valley and northern Italy (called Cisalpine Gaul by the Romans) were inhabited by Celtic speakers who founded cities like Milan. Later, the Romans were defeated at the Battle of Allia, and Rome was sacked by the Senones in 390 BC.

At the Battle of Telamon in 2

Romanisation

Under Caesar, the Romans took control of Celtic Gaul, and starting with Claudius, the Roman Empire included parts of Britain. Roman local government in these areas was similar to the tribal boundaries that existed before the Romans arrived. Archaeological discoveries show that native people were involved in local government.

The people living under Roman rule became more like the Romans and wanted to follow their customs. Celtic art already showed influences from classical styles, and Gallo-Roman artwork either showed classical themes or kept old traditions even with Roman influences.

The Roman rule over Gaul, and to a smaller degree Britain, caused a blending of Roman and Celtic cultures. For the Celts on the mainland, this led to a change in language to Vulgar Latin, while the Celts in Britain kept their language.

Gaul also had a strong influence on Rome, especially in military practices and horse riding. Gauls often worked as soldiers in the Roman cavalry. The Romans used the Celtic cavalry sword called the spatha and adopted Epona, the Celtic goddess of horses.

Society

Sources show that before the arrival of Christianity, Celtic societies in the Iron Age were organized around class and kingship. This system may have developed later in some areas. Roman writers, like Caesar, described relationships between leaders and followers in Gaul that were similar to those in Roman society.

Most evidence suggests that tribes were led by kings. However, some scholars believe that in regions near Rome, different forms of government, such as rule by a group of leaders, may have appeared over time. Celtic societies were often divided into three groups: warriors and leaders, intellectual figures like druids, poets, and judges, and the general population. In Ireland and Scotland, kings were chosen through a system called tanistry, which sometimes conflicted with the Roman idea of passing leadership to the eldest son.

Little is known about how Celtic families lived. Settlements varied, with some communities living in small villages and others in larger towns. In Britain and Ireland, many people lived in hillforts, but in other areas, such as the Hallstatt and La Tène regions, towns and trade centers were common.

Slavery among the Celts likely worked like it did in ancient Greece and Rome. Slaves were captured in wars, raids, or through debt. Slavery could be passed down through families, but some slaves were freed. The Celtic words for "slave" are similar to the Latin word for "captive," showing early contact between Celtic and Roman cultures. In the Middle Ages, slavery was common in Celtic lands, and laws made it hard for slaves to gain freedom.

Very few written records from before Christianity were written in Celtic languages. Most inscriptions used the Roman or Greek alphabets. The ogham script, a special writing system used in Ireland and Scotland, was mainly used for ceremonial purposes like gravestones. Celtic traditions relied heavily on oral storytelling, which was later recorded by monks. Celtic art is known for detailed metalwork, preserved through burial practices.

The Atlantic Celts kept some old traditions, such as using chariots in battle long after other cultures stopped. Despite this, their chariot tactics helped defend against Julius Caesar’s attacks on Britain.

According to Diodorus Siculus, the Gauls were tall, muscular, and had light skin and naturally blond hair. They used lime water to make their hair even lighter and styled it to look like horses’ manes. Some men shaved their beards, while others let them grow. Nobles often shaved their cheeks but grew mustaches.

During the later Iron Age, the Gauls wore long tunics and trousers made of wool or linen. Wealthy people used silk. Cloaks were worn in winter. Jewelry like brooches and armlets were common, but the most famous item was the torc, a metal collar. The Waterloo Helmet, now in the British Museum, was likely used for ceremonies, not battle.

Archaeological findings show that Celtic societies were connected to trade routes across Eurasia. Large roads built over bogs in Ireland and Germany suggest they were used for wheeled transport. The Celts had access to tin, lead, iron, silver, and gold. Their metalworkers made weapons and jewelry for trade, especially with the Romans.

The idea that the Celts only used barter is incorrect. Their money system was complex and not fully understood. Early forms of money, like bronze items shaped like axes or rings, were used. Gold, silver, and bronze coins were also made, with gold being more common than silver. As the Romans expanded, silver and bronze coins became more common, and gold production increased to meet Roman demand.

Few sources describe how the Celts viewed gender roles. Some evidence suggests their views may have been different from those of the Greeks and Romans. Some burials in Gaul show women may have had roles in warfare, but this is not certain. Some graves contained both weapons and female jewelry, but it is unclear if the individuals were male or female. These items may have indicated high social rank rather than gender.

Most written records about the Celts come from Roman and Greek writers. These accounts may not always be accurate. Roman historians noted that Celtic women sometimes led or participated in battles. Plutarch wrote that women acted as diplomats to prevent wars among Celtic groups. Greek writer Posidonius described the Celts as wild, fierce, and having strong, brave women. Other writers, like Cassius Dio, also commented on their customs.

Warfare and weapons

Tribal warfare was a common occurrence in Celtic societies. Ancient stories often describe this as a form of competition focused on raids and hunting, rather than planned battles for land. However, historical records show that Celtic tribes used warfare to gain political power, bother enemies, gain wealth, and sometimes take over land.

Classical writers such as Strabo, Livy, Pausanias, and Florus described the Celts as fighting like "wild beasts" and as large groups. Dionysius wrote that their fighting style was wild and chaotic, lacking organized military strategy. He described how they would swing their swords like wild boars, using their full body strength, and sometimes strike randomly, aiming to harm their opponents completely.

Polybius noted that the main weapon of the Celts was a long sword used for swinging sideways rather than stabbing. He and Plutarch wrote that Celtic warriors often had to stop fighting to straighten their swords. Some archaeologists have questioned this claim, pointing out that Noric steel, a type of high-quality steel made in Celtic Noricum, was used by the Roman military. However, Radomir Pleiner, in The Celtic Sword (1993), argued that evidence shows Polybius was correct in part, as about one-third of surviving swords from that time may have behaved as he described. In addition to swords, the Celts also used spears and special javelins in battle.

Polybius also wrote that some Celts fought without clothing. He described these warriors as a frightening sight because they were strong and in their prime. Livy added that this was also true of Celts in Asia Minor.

The Celts were known for collecting enemy heads. Paul Jacobsthal wrote that the Celts valued human heads above all else, seeing them as symbols of the soul, life, and divine power. Greek historians Posidonius and Diodorus Siculus wrote that Celtic warriors removed the heads of enemies they killed in battle, hung them on their horses, and displayed them at their homes. Strabo wrote that Celts preserved the heads of important enemies in cedar oil and displayed them. Livy recorded that the Boii, a Celtic group, beheaded a Roman general after a battle, covered his skull with gold, and used it as a ceremonial cup. Archaeologists have found evidence that southern Gauls preserved and displayed human heads.

At the Celtic site of Entremont, a pillar with carved skulls was found, containing spaces where human skulls were placed. A nearby site called Roquepertuse had similar carvings and skull niches. Many separate carved heads have been discovered in Celtic regions, some showing two or three faces. Examples include the Mšecké Žehrovice Head and the Corleck Head.

Severed heads appear often in Celtic myths. Stories describe heads that speak or preside over feasts. The beheading game is a common theme in Irish and Arthurian legends, such as in Sir Gawain and the Green Knight, where the Green Knight picks up his own head after being beheaded. There are also tales of Celtic saints who carried their own severed heads. In Irish myths, the heads of fallen warriors are called the "mast" or "nuts" of the goddess Macha.

Religion and mythology

The Celts, like other European Iron Age societies, believed in many gods and thought there was life after death. Their religion changed over time and in different areas, but it shared some basic similarities across Celtic groups. Because the ancient Celts did not write down their beliefs, information about their religion comes from archaeological findings, writings by Greek and Roman people, and early Christian texts.

More than 200 names of Celtic gods have been recorded, though many may have been different names for the same god or used in specific regions. Some gods were only worshipped in one place, while others were known widely. According to Miranda Aldhouse-Green, the Celts also believed that spirits lived in nature, such as in trees, rivers, and animals.

The Celts likely had a god who was a father figure, associated with tribes and the dead (possibly called Toutatis), and a goddess who represented the land, fertility, and motherhood (possibly called Dea Matrona). This goddess could also act as a protector of her people in battle. Another important god was Taranis, linked to thunder and the wheel. Other gods included Lugus, a god of skills and crafts, and Gobannos, a god of metalwork. Healing gods like Sirona and Borvo were connected to sacred springs. Other widely known deities included Cernunnos, a horned god; Epona, a goddess of horses and fertility; and Maponos, a divine son. Julius Caesar wrote that the Gauls believed all people came from a god of the underworld. The idea of three parts, or "triplicity," was common in Celtic beliefs, as seen in the "Three Mothers."

Religious ceremonies were led by priests called druids, who also acted as judges, teachers, and keepers of knowledge. Some druids performed sacrifices for the community. Evidence shows that the Celts sacrificed animals, usually livestock or working animals. Some were fully given to the gods (by burning or burying), while others were shared between humans and gods (part eaten, part offered). There is also some evidence that humans were sacrificed, with Roman sources claiming that criminals were burned inside wicker figures.

The Romans described Celtic religious rituals as taking place in sacred groves and natural shrines called nemetons. Some Celtic groups built temples or ritual enclosures, like the Romano-Celtic temple and viereckschanze, while others used natural sites for worship. People often made votive offerings, such as valuable items left in water, wetlands, or ritual pits, sometimes for many years. Modern clootie wells may be a continuation of this practice.

Most surviving Celtic myths belong to the Insular Celtic peoples, with Irish mythology having the largest collection, followed by Welsh mythology. These stories were written down during the early Middle Ages by Christian scribes.

In Irish mythology, the supernatural group called the Tuatha Dé Danann are believed to represent the main gods of Ireland. Their enemies, the Fomóire, were defeated in the Battle of Mag Tuired. Barry Cunliffe noted that Irish myths often showed a balance between a male tribal god and a female goddess of the land. The Dagda was the main god, and the Morrígan was his partner, both having other names. A common theme was the sovereignty goddess, who symbolized the land and gave a king power by marrying him. The goddess Brigid was linked to nature, poetry, healing, and metalwork.

Some characters in medieval Celtic myths have parallels in ancient European stories. For example, Irish Lugh and Welsh Lleu are related to the god Lugus, and Goibniu and Gofannon are connected to Gobannos. Macán and Mabon are linked to Maponos, while Macha and Rhiannon may be similar to Epona.

In Celtic myths, the Otherworld is a spiritual realm where gods live. Heroes sometimes reached it by entering burial mounds, caves, or by crossing the western sea. Irish myths describe the dead traveling to the house of Donn (Tech Duinn), which matches Caesar’s account that the Gauls believed all people came from a god of the underworld.

Insular Celtic peoples celebrated four seasonal festivals: Beltaine (May 1), Lughnasa (August 1), Samhain (November 1), and Imbolc (February 1).

The Roman invasion of Gaul brought many Celts into the Roman Empire. Roman culture greatly influenced Celtic tribes under Roman control. One major change was the decline of the druid class, which eventually disappeared. New gods, called Romano-Celtic deities, emerged, combining Roman and Celtic traits. Other changes included the use of stone monuments to represent gods and goddesses, as the Celts previously used wooden statues or tree carvings.

When the Roman Empire adopted Christianity, regions under Roman rule also converted. In areas not conquered by Rome, like Ireland and Scotland, people began moving from polytheism to Christianity in the 5th century. Missionaries from Britain, such as Saint Patrick, helped spread Christianity in Ireland. Later, Irish missionaries played a key role in spreading the faith to Scotland, parts of Britain, and central Europe (Hiberno-Scottish mission). Celtic Christianity, which developed in Britain and Ireland, had limited contact with Rome and other Christian traditions for many years. It retained some unique practices, such as its method of calculating Easter. In 664, the Synod of Whitby helped align Celtic Christianity with Roman practices, which had been introduced to Anglo-Saxon England by the Gregorian Mission.

Genetics

Genetic studies of the small amount of material available show a connection between Iron Age people from areas known as Celtic and the earlier Bell Beaker culture of Bronze Age Western Europe. Like the Bell Beakers, ancient Celts had a large amount of ancestry from Western Steppe Herders, a group linked to Yamnaya pastoralists who moved west from the Pontic–Caspian steppe during the late Neolithic and early Bronze Age. This ancestry was especially common among Celts in Northwest Europe. Most studied individuals had a type of genetic marker called paternal haplogroup R-M269, while maternal haplogroups H and U were often found. These markers are linked to steppe ancestry. The movement of Celts into Iberia and the rise of the Celtiberians is connected to an increase in ancestry from north-central Europe in Iberia, possibly tied to the spread of the Urnfield culture. The paternal haplogroup I2a1a1a has been found among Celtiberians. There was likely significant genetic exchange between Celtic groups in Western Europe during the Iron Age. The Gauls in southern France show genetic links to Celtiberians, while the Gauls in northern France are linked to populations in Great Britain and Sweden. Modern people in Western Europe, especially those who speak Celtic languages today, share strong genetic similarities with Iron Age populations from the same regions.