The Celts were a group of people in Europe and Anatolia who shared similar languages and cultures. They included groups such as the Gauls, Celtiberians, Gallaeci, Britons, Picts, Gaels, Boii, and Galatians. Scholars debate how much these groups were connected by shared ethnicity, language, and culture. Today, the term "Celt" usually refers to people who spoke Celtic languages rather than a single ethnic group.

The origins of the Celts are still being studied. One theory, called "Celtic from the East," suggests that the early Celtic language developed in central Europe during the Bronze Age, in a culture known as the Urnfield culture. This theory connects the Celts to later Iron Age cultures like the Hallstatt and La Tène cultures, which spread Celtic influence across Europe. Another theory, "Celtic from the West," claims the early Celtic language began in coastal areas of western Europe and spread eastward. A third theory, "Celtic from the Centre," suggests the language started in central Europe and spread in multiple directions. By the 3rd century BC, Celtic culture had reached as far east as central Anatolia in modern-day Turkey.

The earliest known Celtic writing comes from the Lepontic inscriptions of the 6th century BC. Most Celtic languages on the European mainland are known only from inscriptions and place names. In Britain and Ireland, Celtic languages are recorded from the 4th century AD in Ogham inscriptions, though they were spoken earlier. Celtic literature began with Old Irish texts from the 8th century AD. Stories about Celtic gods and myths appear in early Irish and Welsh writings. Much of what is known about the Celts comes from writings by Greek and Roman authors, who often described them as uncivilized tribes. The Celts followed a religion led by druids.

The Celts often fought against the Romans, as seen in battles like the Roman–Gallic Wars and the conquest of Gaul and Britain. By the 1st century AD, most Celtic lands were part of the Roman Empire. By around 500 AD, Celtic culture had mostly disappeared from mainland Europe due to Roman influence and the arrival of Germanic tribes. It remained strong in Ireland, western and northern Britain, and Brittany. From the 5th to 8th centuries, Celtic-speaking communities in these regions developed a shared culture, language, and traditions.

Over time, Insular Celtic culture split into two main groups: the Gaels (including Irish, Scots, and Manx speakers) and the Celtic Britons (including Welsh, Cornish, and Breton speakers). A modern sense of Celtic identity began 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 traditional regions. Cornish and Manx are being revived after falling out of use.

Names and terminology

The first known use of the name "Celts" was by the Greek geographer Hecataeus of Miletus in 517 BC. He wrote about a group of people living near Massilia (modern-day Marseille) in southern Gaul. In the fifth century BC, the Greek writer Herodotus mentioned the Keltoi living near the source of the Danube River and in western Europe. The origin of the word "Keltoi" is not clearly understood. Some possible roots include a Proto-Indo-European verb meaning "to hide" or "to heat," or a Proto-Celtic word *kel-o-. The name "Celt" appears in the names of ancient Gauls, such as Celtillus, who was the father of Vercingetorix. Linguist McCone (2006) suggests the name might mean "the people or descendants of the hidden one," linking it to the Gauls' belief in descent from an underworld god. Others think the Greeks created the name; linguist Patrizia de Bernardo Stempel suggests it might mean "the tall ones."

In the first century BC, the Roman leader Julius Caesar wrote that the Gauls called themselves "Celts" in their own language, using the Latin term "Celtae." This shows that the name was used by the Celts themselves, even if others gave it to them first. The Greek geographer Strabo, writing near the end of the first century BC, referred to the "race now called both Gallic and Galatic," and also used the term "Celtica" for Gaul. He also mentioned Celtic people in Iberia, calling them "Celtiberi" and "Celtici." Pliny the Elder noted that "Celtici" was used as a tribal name in Lusitania, a region confirmed by written records found on stones.

The Latin name for the Gauls, "Galli" (plural), may have come from a Celtic word, possibly borrowed into Latin during the Celtic expansion into Italy starting around the fifth century BC. Its root might be Proto-Celtic *galno, meaning "power" or "strength." The Greek name "Γαλάται" (Galatai) likely shares the same origin, referring to the Gauls who settled in Galatia in southeast Europe. The Greek suffix "-atai" might be a grammatical ending. Linguist Kim McCone suggests the name "Galatai" originally described young warrior groups, not the entire people. He notes that the Greeks may have used this term because the Gauls' first interactions with the Mediterranean world often involved fierce young warriors.

Some scholars avoid using the term "Celt" for the people of Britain and Ireland in ancient times because Classical writers did not call them "Keltoi" or "Celtae." However, these people spoke Celtic languages, shared cultural traits, and Roman historian Tacitus noted that the Britons resembled the Gauls in customs and religion.

For at least 1,000 years, no group called itself "Celt" or "Celtic." The term was not used until about 1700 AD, when it was rediscovered in ancient texts. It was then applied to the culture, history, traditions, and language of modern Celtic nations, including Ireland, Scotland, Wales, Cornwall, Brittany, and the Isle of Man. The word "Celt" first appeared in English writing in 1707, in the work of Edward Lhuyd. The English words "Gaul," "Gauls," and "Gaulish" come from French "Gaule" and "Gaulois," which were borrowed from Frankish Walholant, meaning "Roman-land." This term is linked to Proto-Germanic walha-, meaning "foreigner" or "Celt," which is also the root of the English word "Welsh." The name "Walha" comes from the Volcae, a Celtic tribe that lived in Germany and later moved to Gaul.

The term "Celtic" refers to a language family and generally means "of the Celts" or "in the style of the Celts." Several ancient cultures are considered Celtic based on unique artifacts. Inscriptions on objects help connect languages to these cultures. Today, the idea of a Celtic identity focuses on shared languages, art, and traditions, as well as classical texts. Earlier theories suggested a common "racial" origin, but modern views emphasize cultural and linguistic similarities instead of genetic ties. Celtic cultures were diverse, with the common use of Celtic languages being their main shared feature.

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 Celtic languages are Irish, Scottish Gaelic, Welsh, and Breton, with Cornish and Manx being recent revivals. There are also efforts to reconstruct Cumbric, a Celtic language once spoken in northern Britain. In mainland Europe, people in regions like western Iberia (Portugal and parts of Spain) claim a Celtic heritage, though no Celtic languages are spoken there today.

The Celts of mainland Europe are called "Continental Celts," while those from the British and Irish islands are called "Insular Celts." The Celts of Brittany speak a language brought by Insular Celts from Britain, so they are grouped with the Insular Celts.

Origins

The Celtic languages are a group within the larger family of Indo-European languages. When written records first mention the Celts around 400 BC, 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. Over time, these languages split into branches such as Celtiberian, Goidelic, and Brittonic.

For much of the twentieth century, many scholars believed that the Celts and their early language, called proto-Celtic, originated from the Urnfield culture in central Europe around 1000 BC. This culture spread westward and southward over the next few centuries. The Urnfield culture was important in central Europe during the late Bronze Age, from about 1200 BC to 700 BC. Later, the development of iron-working led to the Hallstatt culture (around 800 to 500 BC), which grew from the Urnfield culture in areas north of the Alps. The Hallstatt culture eventually evolved into the La Tène culture, which began around 450 BC and became closely linked to Celtic art.

In 1846, Johann Georg Ramsauer discovered ancient graves with unique items in Hallstatt, Austria. He believed these graves were from the time when the Celts were near the Danube River, as mentioned by the ancient writer Herodotus. This discovery led to the naming of the "Hallstatt culture." In 1857, an archaeological site called La Tène was found in Switzerland. Artifacts from this site had a unique style, and similar items were found in areas where Celts were known to live. By the 1870s, scholars connected these artifacts to the Celts. However, the Roman Empire later took over much of this region, though some La Tène-style designs remained in Gallo-Roman art. In Britain and Ireland, the La Tène style survived in a limited way and later appeared in Insular art.

In the late twentieth century, some scholars began to question the Urnfield-Hallstatt theory. They found that the oldest known Celtic-language writings were from Lepontic (6th century BC) and Celtiberian (2nd century BC), which were found in northern Italy and Iberia. These regions were not part of the Hallstatt or La Tène cultures at the time. The Urnfield-Hallstatt theory also relied on ancient Greek and Roman writings, such as those by Herodotus, which placed the Celts near the Danube. However, some researchers, like Stephen Oppenheimer, noted that Herodotus may have believed the Danube’s source was near the Pyrenees, which aligns more closely with later classical accounts of the Celts living in Gaul and Iberia.

The theory also depended on the presence of Celtic names in the Eastern Hallstatt region (Noricum). However, Patrick Sims-Williams pointed out that these names date to the later Roman era and suggest a late arrival of a Celtic-speaking group.

By the late twentieth century, the Urnfield-Hallstatt theory became less popular as new archaeological discoveries emerged. Scholars began to see "Celtic" as a label for people who spoke Celtic languages, not as a single culture or ethnic group. A new theory suggested that Celtic languages originated earlier, along the Atlantic coast, including Britain, Ireland, Armorica, and Iberia, long before evidence of "Celtic" culture appeared in archaeology. Some researchers, like Myles Dillon and Nora Kershaw Chadwick, proposed that the Celts may have arrived in the British Isles during the Bell Beaker culture of the Copper and Bronze Age (around 2750 BC). Martín Almagro Gorbea (2001) also argued that Celtic languages arose in the 3rd millennium BC, spreading with the Bell Beaker culture across western Europe.

John T. Koch and Barry Cunliffe developed the "Celtic from the West" theory, which suggests that the proto-Celtic language began along the Atlantic coast and spread inland and eastward. Cunliffe later proposed that proto-Celtic may have originated in the Atlantic zone as early as 3000 BC, spreading eastward with the Bell Beaker culture. His ideas are based on glottochronology, the distribution of ancient Celtic-like place names, and the claim that the Tartessian language was Celtic. However, many linguists disagree with the idea that Tartessian was Celtic.

Patrick Sims-Williams (2020) notes that modern scholarship often defines "Celt" primarily as a linguistic group. In his "Celtic from the Centre" theory, he argues that proto-Celtic did not originate in central Europe or the Atlantic but in a region between them. He suggests that it emerged as a distinct Indo-European dialect around the second millennium BC, likely in Gaul (modern France), and spread in various directions during the first millennium BC. This theory avoids the idea that Celtic was spoken over a vast area for a long time without major dialectal changes and aligns Celtic with regions near Italy, where Italic and Celtic languages may have been 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, are in Gaulish and 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, such as Primitive Irish Ogham inscriptions, appears only around 400 AD.

Besides written records, place names (toponymy) provide important information about early Celtic languages.

Arnaiz-Villena et al. (2017) found that populations in the European Atlantic region (Orkney Islands, Scottish, Irish, British, Bretons, Portuguese, Basques, Galicians) share a common HLA system, which may be related to Celtic heritage. However, other genetic studies do not support a strong genetic link between these groups beyond their shared West European ancestry. Early European Farmers settled Britain and other parts of Northern Europe during the Neolithic period. However, genetic research shows that between 2400 and 2000 BC, over 90% of British DNA was replaced by Steppe Herders, who brought large amounts of Steppe DNA (including the R1b haplogroup) to western Europe. Modern genetic studies confirm that both ancient and modern British and Irish populations cluster closely with other North Europeans

Distribution

The Romans called the Celts living in what is now France the Gauls. The area these people lived in likely included the Low Countries, the Alps, and northern Italy. Julius Caesar wrote about the descendants of these Gauls in his book Gallic Wars, which described events from the 1st century BC.

Eastern Gaul became 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 writings from southern Gaul, written in Greek characters, 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 mostly Celtic-speaking population. Rome wanted better land connections to its Iberian provinces and fought a major battle with the Saluvii tribe at Entremont between 124–123 BC. Over time, Roman control expanded, and the Roman province of Gallia Transalpina was created along the Mediterranean coast. The Romans called the rest of Gaul Gallia Comata, meaning “Long-haired Gaul.”

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

After the Gallic Wars from 58–51 BC, Caesar’s Celtica became the main part of Roman Gaul, forming the province of Gallia Lugdunensis. This area, home to Celtic tribes, was bordered 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, such as Belgica and Aquitania, especially under Augustus.

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

Until the late 1800s, scholars believed the Celts were present in the Iberian Peninsula, linked to the Hallstatt and La Tène cultures. However, because the 19th-century definition of the Iron Age made it hard to connect Iberian cultures to Central Europe, their presence was often ignored. Modern research now shows that Celtic influence was strong in what is now Spain and Portugal, especially in central, western, and northern regions.

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

Understanding the origins of the Celtiberians may help explain how Celtic culture spread across the Iberian Peninsula. The Celtic influence in the southwest and northwest was not only due to the Celtiberians. Research on the Callaici and Bracari in northwest Portugal is helping scholars learn more about 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 writing, over 100 years older than other examples.

In Germany, by the late Bronze Age, the Urnfield culture (1300–750 BC) replaced earlier cultures like the Bell Beaker and Unetice. In Scandinavia and northern Germany, the Nordic Bronze Age developed. 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–6th centuries BC). It was followed by the La Tène culture (5th–1st centuries BC).

People who adopted Hallstatt and La Tène cultural traits in central and southern Germany were considered Celts. Celtic cultural centers formed in Central Europe during the late Bronze Age (1200–700 BC). Places like the Heuneburg, an important city north of the Alps, became key trade hubs connected to the Mediterranean. In the 5th century BC, the Greek historian Herodotus wrote about a Celtic city near the Danube and Pyrenees, likely referring 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 was the first wave of proto-Celtic people from the northwest Alps. They settled in the western Po Valley between Lake Maggiore and Lake Como (Scamozzina culture). Some evidence suggests proto-Celtic people were present in northwest Italy as early as the Middle Bronze Age, linked to bronze artifact production similar to the Tumulus culture. La Tène cultural items were found across mainland Italy, with the farthest example being a Celtic helmet from Canosa di Puglia.

Italy is home to Lepontic, the oldest known Celtic language, dating to 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 living beyond the Alps moved through mountain passes and took control of the land between the Apennine Mountains and the Alps. The Po Valley and northern Italy (called Cisalpine Gaul by the Romans) were home to Celtic speakers who founded cities like Milan. Later, the Romans were defeated at the Battle of Allia, and Rome was attacked by the Senones in 390 BC.

At the Battle of Telamon in 225 BC, a large Celtic army was trapped between two Roman forces and destroyed.

The defeat of the combined Samnite, Celtic, and Etruscan alliance by the Romans in the Third Samnite War marked the end of Celtic dominance in mainland Europe. However, it was not until 192 BC that Roman armies conquered the last independent Celtic kingdoms in Italy.

The Celts also expanded along the Danube River and its tributaries. The Scordisci tribe, one of the most influential groups, built their capital at Singidunum (modern-day Belgrade, Serbia) in the 3rd century BC. The Tisza Valley, in present-day Vojvod

Romanisation

Under Caesar, the Romans conquered the Celtic region of Gaul, and starting with Claudius, the Roman Empire included parts of Britain. Roman local government in these areas was similar to the boundaries of tribes 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 ways. Celtic art already included influences from classical cultures, and surviving Gallo-Roman artworks either showed classical themes or kept old traditions even with Roman styles.

The Roman occupation of Gaul, and to a lesser degree Britain, caused a blending of Roman and Celtic cultures. For the Celts on the European mainland, this led to a shift in language to Vulgar Latin, while the Celts in Britain and Ireland kept their language.

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

Society

The sources available describe the social structure of the Celtic people before Christianity, which was based on class and kingship. However, this may have been a later stage of organization in Celtic societies. Relationships between leaders and followers, similar to those in Roman society, are mentioned by Caesar and others in descriptions of Gaul during the 1st century BC.

Most evidence shows that tribes were led by kings. Some argue that in areas near Rome, systems where a group of people made decisions together may have also developed. Descriptions of Celtic societies often divide them into three groups: a warrior class; an intellectual class including druids, poets, and judges; and all other people. In Ireland and Scotland, high and low kings were chosen through a system called tanistry, which later conflicted with the Roman idea of passing leadership to the eldest son.

Little is known about how Celtic families were structured. Settlement patterns varied, with some groups living in scattered villages and others in cities. The common image of non-urban societies living in hillforts and duns, such as the 3,000 known in Britain, contrasts with the cities found in the Hallstatt and La Tène regions. These areas had large settlements called oppida in Gaul and towns in Gallia Cisalpina.

Slavery among the Celts likely worked like 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 Old Irish and Welsh words for "slave," cacht and caeth, are related to the Latin word captus, showing early contact between Celtic and Latin societies. In the Middle Ages, slavery was common in Celtic lands, and laws discouraged freeing slaves. The word for "female slave," cumal, was used as a unit of value in Ireland.

Very few written records from before Christianity exist in Celtic languages. Most are inscriptions using Roman or Greek alphabets. The ogham script, an Early Medieval alphabet, was used in Ireland and Scotland for ceremonial purposes like gravestone inscriptions. Oral traditions, such as those preserved by bards and later recorded by monasteries, were strong. Celtic art produced intricate metalwork, often preserved through burial practices.

Some Atlantic Celts were conservative, such as continuing to use chariots in battle long after they were used only for ceremonies by Greeks and Romans. Despite this, their chariot tactics helped resist Julius Caesar’s attempts to invade Britain.

According to Diodorus Siculus:
The Gauls were tall with strong muscles and fair skin. Their hair was naturally blond, and they used limewater to make it even lighter. They styled their hair to look like Satyrs and Pans, with heavy, coarse hair resembling horse manes. Some shaved their beards, while others let them grow slightly. Nobles shaved their cheeks but let their mustaches grow to cover their mouths.

During the later Iron Age, the Gauls wore long-sleeved tunics and long trousers called braccae by the Romans. Clothes were made of wool or linen, with some silk used by the wealthy. Cloaks were worn in winter. Brooches and armlets were common, but the most famous jewelry was the torc, a metal neck collar. The Waterloo Helmet in the British Museum, often seen in images of Celtic warriors, was likely ceremonial rather than military.

Archaeological evidence shows that pre-Roman Celtic societies were part of overland trade routes across Eurasia. Large trackways found in Irish and German bogs suggest they were used for wheeled transport. The Celts controlled resources like tin, lead, iron, silver, and gold. Their metalworkers produced weapons and jewelry for trade, especially with the Romans.

The idea that the Celts only used barter is incorrect. Their monetary system was complex and not fully understood. "Proto-money," such as bronze items shaped like axeheads, rings, or bells, was likely used. These items were found in burials and may have had high value for daily purchases. Low-value coins made of potin, a bronze alloy, were common before Roman conquest. Higher-value coins, made of gold, silver, and bronze, were also used. Gold was more common than silver, despite being more valuable, because silver was harder to mine. As Rome expanded trade, silver and bronze coins became more common, and Celtic gold production increased to meet Roman demand. This is thought to be a reason for Caesar’s invasion of France.

Few sources describe Celtic views on gender roles, but some evidence suggests they may have been different from Greco-Roman societies. Some Iron Age burials in northeastern Gaul suggest women may have participated in warfare during the La Tène period, though this is not certain. Graves with both female jewelry and weapons, like the Vix Grave, raise questions about the gender of those buried with weapons. It is possible these items indicated high social rank rather than masculinity.

Most written accounts of the Ancient Celts come from Roman and Greek sources, though their accuracy is unclear. Roman historians like Ammianus Marcellinus and Tacitus wrote about Celtic women leading or participating in battles. Plutarch mentions Celtic women acting as diplomats to avoid war. Posidonius described the Celts as primitive, fierce, and having strong, courageous women. Cassius Dio suggested there was…

Warfare and weapons

Tribal warfare was common among Celtic societies. Ancient stories often describe this as a form of competition focused on raids and hunting, not large-scale battles for land. However, historical records show that Celtic tribes used warfare to gain power, pressure rivals, gain wealth, and sometimes take over land.

Classical writers like Strabo, Livy, Pausanias, and Florus described the Celts as fighting like "wild beasts" and as large groups of warriors. Dionysius wrote that their fighting style was unpredictable and lacked military strategies. He said they would swing their swords like wild boars, using their full body strength, or strike randomly, aiming to harm enemies completely.

Polybius noted that the main weapon of the Celts was a long sword used for slashing rather than stabbing. He and Plutarch wrote that Celtic warriors often had to stop fighting to fix their swords. Some archaeologists question this, pointing out that Noric steel, made in Celtic Noricum, was highly valued by the Romans and used by their army. However, Radomir Pleiner, in The Celtic Sword (1993), argued that evidence from metal studies 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.

Polybius also wrote that some Celts fought without clothing, describing them as a terrifying sight because they were strong and young. Livy confirmed this was true for Celts in Asia Minor.

The Celts were known for taking enemy heads. Paul Jacobsthal wrote that the Celts believed the head represented the soul, emotions, and life itself, and was a symbol of divinity. Greek historians Posidonius and Diodorus Siculus wrote that Celtic warriors removed the heads of fallen enemies, hung them on their horses, and displayed them at home. Strabo wrote that Celts preserved the heads of respected enemies in cedar oil and displayed them. Livy recorded that the Boii, a Celtic group, beheaded a Roman general after a battle, gilded his skull, and used it as a ritual cup. Archaeologists have found evidence that southern Gauls embalmed and displayed enemy heads.

At the Celtic site of Entremont, a pillar with carved skulls was found, containing niches where human skulls were placed. A nearby site, Roquepertuse, had similar carvings and skull niches. Many carved heads have been discovered in Celtic regions, some with multiple faces, such as the Mšecké Žehrovice Head and the Corleck Head.

Severed heads appear often in Celtic myths. In stories, heads are shown at feasts or speaking prophecies. The "beheading game" appears in Irish and Arthurian legends, such as in Sir Gawain and the Green Knight, where the Green Knight retrieves his own severed head after being struck by Gawain. Celtic legends also include stories of saints who carried their own severed heads. In Irish myths, the severed heads of warriors were 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 the Celtic peoples. Since the Celts did not have a writing system, information about their religion comes from archaeological findings, writings by Greeks and Romans, and texts from the early Christian era.

Over 200 names of Celtic gods have been recorded, though many may have been different names or titles for the same god. Some gods were worshipped in specific regions, while others were known more widely. According to Miranda Aldhouse-Green, the Celts also believed that spirits lived in nature, a belief called animism.

The Celts likely had a father god, often associated with tribes and the dead (possibly named Toutatis), and a mother goddess linked to the land, fertility, and earth (possibly named Dea Matrona). This goddess could also appear as a protector of her people in battle. A male god connected to the sky, thunder, and the bull was named Taranis. Other gods included Lugus, a god of skills and crafts, and Gobannos, a god of metalwork. Healing gods like Sirona and Borvo were linked to sacred springs. Other widely known deities included Cernunnos, a horned god; Epona, a goddess of horses and fertility; Maponos, a divine son; and Belenos, Ogmios, and Sucellos. Caesar noted that the Gauls believed all people descended from a god of the dead and underworld. Triplicity, or the idea of three parts, was common in Celtic beliefs, as seen in the "Three Mothers" concept.

Celtic 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’s benefit. Evidence shows that Celts sacrificed animals, usually livestock, by burying or burning them entirely or sharing them between gods and humans. Some sources suggest that humans were also sacrificed, with the Gauls reportedly burning criminals in wicker figures.

The Romans described Celtic ceremonies as taking place in sacred groves and natural shrines called nemetons. Some Celts built temples or ritual enclosures, such as Romano-Celtic temples and viereckschanzen, while others honored gods at natural sites. Votive offerings—treasured items placed in water, wetlands, or ritual pits—were common, a practice possibly reflected in modern clootie wells.

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

In Irish mythology, the supernatural group called the Tuatha Dé Danann represents the main gods of Ireland. They fought the Fomóire in the Battle of Mag Tuired. Barry Cunliffe noted that Irish myths often contrast a male tribal god with a female goddess of the land. The Dagda was the chief god, and the Morrígan was his partner, each with other names. A common theme is the sovereignty goddess, who symbolizes the land and grants kingship by marrying a king. The goddess Brigid was linked to nature, poetry, healing, and metalwork.

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

In Insular Celtic myths, the Otherworld is a spiritual realm where gods live. Heroes often reach it by entering burial mounds, caves, or crossing the western sea, or by accepting a silver apple branch from an Otherworld resident. Irish myths describe the dead traveling to the house of Donn (Tech Duinn), a legendary ancestor, echoing Caesar’s claim that the Gauls believed all people descended from a god of the dead and underworld.

Insular Celts 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, especially weakening the druid class, which eventually disappeared. Romano-Celtic deities combined Roman and Celtic traits, and stone monuments began to replace wooden images used before the Roman conquest.

As the Roman Empire adopted Christianity, unconquered areas of Ireland and Scotland gradually shifted from polytheism to Christianity by the 5th century. Missionaries from Britain, like Saint Patrick, converted Ireland. Later, Irish missionaries spread Christianity to Scotland, Anglo-Saxon regions, and central Europe (see Hiberno-Scottish mission). Celtic Christianity, which developed in Britain and Ireland, had limited contact with Rome and other Christian traditions for centuries. It retained unique practices, such as a different way of calculating Easter. The Synod of Whitby in 664 helped align Celtic Christianity with Roman practices introduced by the Gregorian Mission to Anglo-Saxon England.

Genetics

Studies of genetic material show that people from the Iron Age in areas considered Celtic are connected to the Bell Beaker culture of Bronze Age Western Europe. Like the Bell Beaker people, ancient Celts had a significant amount of genetic heritage from Western Steppe Herders. This heritage comes from Yamnaya pastoralists who moved westward from the Pontic–Caspian steppe during the late Neolithic and early Bronze Age. This movement is linked to the spread of Indo-European languages. This type of heritage was especially common among Celts in Northwest Europe. Most studied individuals had a type of paternal genetic marker called R-M269, while maternal markers H and U were often found. These markers are connected to steppe heritage. The movement of Celts into Iberia and the rise of the Celtiberians is linked to an increase in genetic traits from north-central Europe in Iberia. This may be related to the spread of the Urnfield culture. A paternal genetic marker called I2a1a1a has been found among Celtiberians. There was likely a lot of genetic exchange among Celtic groups in Western Europe during the Iron Age. The Gauls in southern France share genetic links with Celtiberians, while the Gauls in northern France share links with people from Great Britain and Sweden. Modern populations in Western Europe, especially those who speak Celtic languages, have strong genetic connections to Iron Age populations in the same regions.