4 Celtic Warriors Who Became Figures of Legend

The Celts were famed for their prowess in war. Unsurprisingly, certain particularly impressive Celtic warriors became figures of legend. But which ones? And how did their actions become legendary?

Feb 2, 2023By Caleb Howells, BA Doctrines and Methodology of Education

brennus sculpture bust celtic warriors illustration


The Greeks and Romans had much to say about the Celts. One of the most notable things about Celtic warriors was that they were exceptionally ferocious in warfare. For this reason, they were not easy for the Romans to defeat.


Celtic warriors were not primitive savages. Yet, because the Romans often referred to them as “barbarians”, that is what many people today imagine them to have been. In reality, many Celtic warriors were powerful chieftains, or even kings, who ruled over thousands of people.


Some of these warriors, who were both mighty in warfare and politically important, and came to be remembered by subsequent generations. They left an indelible mark on their culture, causing to legends to grow around them.


1. Boudicca: Powerful Queen and Celtic Warrior

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Boadicea Haranguing the Britons, John Opie, c. 1793, via Wikimedia Commons


Boudicca is one of the most famous Celtic warriors of all time. She lived in the first century CE, not long after the Roman conquest of southern Britain. Roman rulership over these Celtic tribes had not been going on for long, so it was politically a much more fragile situation than later on in Roman Britain. Within this politically fragile environment, Boudicca led a revolt against the Roman government.

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Her attacks were highly successful. She was said to have killed many tens of thousands of people. This Celtic warrior even managed to burn down the city of London. Yet, despite her initial successes, her rebellion was put down by the Romans, and she was executed.


Her activities were remembered some five centuries later when the British writer Gildas wrote about her in his De Excidio. Although he does not mention her by name, it is certainly her that he was referring to when he mentions a “treacherous lioness”. He was not merely describing a female political leader, as his description of her activities makes clear. He says that she “butchered the governors who had been left” by the Romans. This certainly matches what we know about Boudicca and her ferociously violent actions against the Romans. The mention appears early in Gildas’ account of Roman Britain, so the chronology also matches Boudicca.


Notably, Gildas does not mention any other Celtic warriors rising up against the Romans in Britain, although we know that there were others. It is evident that Boudicca left a powerful mark on the history of the Britons.


2. Brennus: Sacker of Rome

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Bust of Brennus, by the Toulon Sculpture workshop, via magnaeceltae.com


Brennus had an even greater impact on history than Boudicca, although he is not as famous today. He was a Celtic warrior who ruled over the Senones, one of the tribes of Gaul, in the early fourth century BCE. As a powerful chieftain, he led his army down through Italy and into Rome itself in about 390 BCE. He defeated the Roman army and sacked the city, burning it to the ground.


Brennus held Rome for several months. However, his army was eventually repelled from the city. There are differing accounts of how this happened. Some claim that the Romans defeated them in battle, while others say that the Celts accepted tribute after being weakened by disease. In any case, the actions of this Celtic warrior were significant. The sacking of Rome caused the destruction of the city records, meaning that all reliable information about the early years of Rome were lost forever. Apart from this consequence, his attack against Rome was part of a general policy of outward expansion. This expansion of the Celts, particularly to the east, would end up having a powerful impact on the history of the Balkans and western Anatolia.


geoffrey of monmouth page text
Page from The History of the Kings of Britain, by Geoffrey of Monmouth, via the British Library


A major source for our knowledge of Celtic legends is the Historia Regum Britanniae, written by Geoffrey of Monmouth in about 1137 CE. Although it is often dismissed as unreliable because of the claim that Geoffrey simply invented stories, the reality is more complicated. Regardless of whether he was adding details to stories, he was certainly working primarily from tales that were genuinely circulating Britain.


One major episode that features in this book is the attack of Rome by a king named Brennius. Geoffrey describes how Brennius was the brother of Belinus, the king of Britain. Together, they led an army of Gauls and Britons to Italy, where they attacked Rome. They successfully defeated the Romans and Brennius ruled the city from then on.


Although this story is clearly describing the historical event involving Brennus’ attack on Rome, many of the details are very different and evidently confused. It is clear that Geoffrey had not just taken the story from the Roman historians who wrote about it. Rather, this was evidently a garbled tradition, a genuine legend.


3. Cassivellaunus

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Julius Caesar, by Peter Paul Rubens, 1625/6, via The Leiden Collection


Cassivellaunus was a powerful king in Britain who lived in the first century BCE. He ruled over a large region in the southeast, over the Catevallauni tribe. When Julius Caesar invaded Britain in 55 BCE, many of the tribes in the southeast temporarily united under the leadership of Cassivellaunus. The events of 55 BCE were swiftly resolved with a retreat from the Romans.


However, in the following year, Julius Caesar returned. One factor involved in his return was that another king named Mandubracius had been driven out of his kingdom by Cassivellaunus. Mandubracius fled to Caesar and asked him to restore him to his kingdom. Caesar was able to accomplish this and managed to subdue Cassivellaunus into surrendering. However, it was not a total victory. Caesar was not able to actually conquer any territory, although he did exact tribute from the Britons.


geoffrey of monmouth wood sculpture
Statue of Geoffrey of Monmouth, Tintern, Monmouthshire, via Wikimedia Commons


It is not surprising that the first Celtic warrior in Britain to fight against the Romans was remembered by his people. Over a millennium later, he appeared in Geoffrey of Monmouth’s Historia Regum Britanniae. The account is thoroughly distorted, but it is still recognizably Cassivellaunus, although his name is spelled “Cassibelaunus”.


In this account, the powerful Celtic warrior is the uncle of Mandubracius, whose name is spelled Androgeus. Historically, we have no confirmation of Cassivellaunus being the uncle of Mandubracius. Nevertheless, the legend presents Cassibelaunus as driving Androgeus out of Britain, which does reflect what really happened with Mandubracius.


In the legend, the reason given is that Androgeus’ nephew had killed the nephew of Cassibelaunus, leading the latter to declare war on Androgeus. Again, there is no historical confirmation of this series of events. But most importantly, the legend preserves the reality of Cassivellaunus leading the Britons against the Romans but then ultimately surrendering.


This same Celtic warrior also appears in another British legend. This legend is part of a collection of tales known as the Mabinogion. In the Second and Third Branches of the Mabinogion, Cassivellaunus’ tale is told. His name appears here (and in other Welsh records) as “Caswallawn”. In this Welsh legend, Caswallawn usurps the throne from the rightful heir, Manawydan, while the latter is away in Ireland. He uses a magic cloak that turns him invisible to accomplish this, killing the men left in charge by the king.


Later, some of those who had been loyal to the previous dynasty submit to Caswallawn in an attempt to avoid any further bloodshed. It is probable that this legend about Caswallawn usurping the throne comes from the historical Celtic warrior driving Mandubracius out of Britain.

4. Niall of the Nine Hostages

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Illustration of Irish soldiers, by Albrecht Dürer, 1521, via Vitantica.net


Niall of the Nine Hostages is very important to Irish history. Unlike the other Celtic warriors in this article, the historical facts about Niall are shrouded in mystery. In fact, even his very historicity is questioned, although the majority of scholars do agree that he was likely a real person.


What can be said about him historically is that he likely lived in the first half of the fifth century CE. This Celtic warrior may have been a member of the dynasty of Ulster in Ireland. Some scholars have suggested that the kingdoms of Tír Chonaill, Tír Eoghain, and Airgíalla emerged from the fragmentation of Ulster in the time of Niall. It is also believed that Niall, as a powerful Celtic warrior, led raids against Britain. It was likely on one of these raids that he died. His descendants then continued ruling over parts of Ireland until the 10th century.


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Illustration of Irish warriors, c. 1547, via irisharchaeology.ie


In the legendary sources that describe this Celtic warrior, his reign is placed in the late fourth to the early fifth century. Our information about Niall’s sons and when they lived shows that this dating is too far in the past. This extended chronology was likely created to push Saint Patrick’s life as far back as possible since Patrick was said to have been abducted by Niall.


In legends, Niall was one of five brothers, sons of the High King of Ireland. The available accounts differ as to how it happened, but somehow, Niall became the High King of Ireland after his father’s death. His brothers became local kings beneath his sovereignty. He is portrayed as a truly mighty Celtic warrior. According to one Irish poem, found in Lebor na hUidre, he traveled to the Alps seven times. One version of the story of his death actually describes how Niall was killed during a campaign that took place through Europe as far as that mountain range. However, there is reason to believe that the story originally referred to either Scotland or Britain, both of which were sometimes known as “Alba” (compare to “Alps”).


Celtic Warriors Who Became Legends

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Illustration of Celtic warrior, Angus McBride, via about-history.com


There were many Celtic warriors throughout history. The most prominent of them left such a strong mark on their kinsmen that legends grew around them. Boudicca was one of the most well-remembered Celtic warriors from Roman Britain, being the only one mentioned by Gildas in the sixth century. Brennus, the chieftain of a Gallic tribe, left an indelible mark all the way over in Britain for his successful attacks against Rome. Cassivellaunus was the first Celtic warrior in Britain to lead his people in the fight against the Romans. Unsurprisingly, he became remembered for his exploits in that war. Finally, Niall of the Nine Hostages was very likely a historical king who raided outside of Ireland, for which exploits he became a figure of legend.

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By Caleb HowellsBA Doctrines and Methodology of EducationCaleb is a published history author with a strong interest in ancient Britain and the Mediterranean world. He holds a BA in the Doctrines and Methodology of Education from USILACS. He is the author of "King Arthur: The Man Who Conquered Europe" and "The Trojan Kings of Britain: Myth or History?". Caleb enjoys learning about history in general, but he especially loves investigating myths and legends and seeing how they might be explained by historical events and individuals.