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Aurelius Ambrosius: The Uncle of King Arthur?

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Relatively few characters from the Arthurian legends can be definitely confirmed as historical. Aurelius Ambrosius is one of them. He was Arthur’s legendary uncle and he had a large part to play in the founding of Arthur’s dynasty and also in the war against the Saxons.

In this article, you will learn:

  • Who Aurelius Ambrosius is
  • About his family
  • The fictional history behind him
  • Whether he is a historical figure

See our complete list of Arthurian characters for more entries like this one.

Family of Aurelius

Aurelius Ambrosius

The earliest account which gives direct details about Ambrosius’s lineage is the Historia Brittonum of the ninth century. Ambrosius is mentioned several times in this work. One of them makes a reference to his father being a consul.

This ties in with an even earlier reference by the sixth century Gildas to Ambrosius’s parents having ‘worn the purple’. Purple was a color that was worn by those in various different prominent positions in the Roman Empire, including consuls.

So the claim from Historia Brittonum about Ambrosius’s parentage is plausible.

Connection to His Father Constantine

The next source to give more information about Ambrosius’s family is Geoffrey of Monmouth’s 12th century Historia Regum Britanniae.

According to this, his father was Constantine, the king of Britain. This character is traditionally identified as the historical Constantine III, the usurping emperor of Britain and Gaul in the early fifth century (however, there are reasons for doubting this identification).

An emperor could also be a consul, and Constantine III did hold that position in 409.

Alternative Theories on Ambrosius’s Father

On the other hand, if Ambrosius’s father was actually a different Constantine who ruled as some kind of king in Britain in the early fifth century, then he could well have been a consul within Britain (for there is evidence that the Britons kept the position of consul even after they broke away from the Roman Empire).

In any case, Ambrosius’s father was allegedly named Constantine, whether that was the historical Constantine III or a different man of the same name.

Ambrosius’s Siblings

According to the HRB, Ambrosius was the middle of three brothers. His older brother was Constans, while his younger brother was Uther.

Constans spent his youth as a monk. However, after his father was killed, he became the king of Britain. Sometime later, he was also killed, murdered by Vortigern.

At this point, Ambrosius and his brother Uther were taken away to Britanny for protection, and this is where Ambrosius grew up.

Ambrosius’s Marriage and Descendants

There is no direct record in any legend of Ambrosius marrying and having children. However, Gildas mentions his descendants in his time, so we know that he must have had children.

Relationship to King Arthur

Ambrosius’s younger brother Uther was, of course, the father of King Arthur. This makes Ambrosius the paternal uncle of Arthur.

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The Story of Aurelius Ambrosius

The following tells the tale of Aurelius Ambrosius, some parts of which may be based in fact, while most of it is likely fictional.

The Tower of Vortigern

One particularly famous episode in the Historia Brittonum concerns the building of a tower by Vortigern’s men.

In this account, a young boy is brought to the tower to be sacrificed so as to stop the tower from constantly collapsing, but he manages to outwit Vortigern’s wise men by progressively revealing what is underneath the tower and actually causing it to collapse.

The boy tells his name to Vortigern, revealing that he is Ambrosius.

In this source, the young Ambrosius is found in and taken from Glywysing (roughly modern-day Glamorgan). Thus, it is likely that Ambrosius’s family had some connection with this area.

Western Britain and Ambrosius’s Victory

At the end of the account, Vortigern cedes all of western Britain to Ambrosius. This perhaps indicates that the origin of this fanciful encounter was a real battle between of some kind between a young Ambrosius and Vortigern’s forces.

Battle with Vitalinus

Interestingly, the Historia Brittonum records a battle between Ambrosius and a man named Vitalinus. This is said to have taken place in 437.

This would have had to have been when Ambrosius was young, probably in his late teens (see ‘When He Lived’ below).

The identity of Vitalinus is difficult to ascertain, but he appears to be connected to Vortigern in some way (a form of the name appears as the name of Vortigern’s father and grandfather in the HB, indicating that it was a family name).

Therefore, the fanciful story of Vortigern and the young Ambrosius, which ends in Vortigern ceding a large portion of Britain to the youth, might come from this historical encounter between a teenage Ambrosius and the forces of Vortigern in 437, resulting in a victory for Ambrosius.

Return to Brittany and Nominal Control

Nonetheless, the HRB claims that Ambrosius grew up in Brittany and only permanently returned when he began his campaign against the Saxons and slew Vortigern (which, as we will see later, took place well into the second half of the fifth century).

So it appears that Ambrosius might have returned to Brittany soon after this victory against Vitalinus, holding only nominal control over western Britain, or a large portion thereof.

Avenging the Massacre and Defeating Vortigern

After the massacre of the British leaders by the Saxons, Ambrosius decided to return to Britain to avenge this massacre.

He and his brother Uther returned and fought very effectively against their enemies. Firstly, they attacked Vortigern, pursuing him to his castle in Wales.

They burned the castle to the ground, killing Vortigern.

Campaign Against the Saxons

After this, Ambrosius and Uther began a campaign against the foreign invaders. The Saxons were in fear of the British leader, and they fled to the north, past the Humber.

Ambrosius won the following battle, though Hengist (the Saxon leader) was still alive and managed to reposition his army elsewhere. At the second battle, Ambrosius was able to win with the help of troops from Brittany.

After killing Hengist, he pardoned the two other Saxon leaders, Octa and Eosa, after they submitted to his rule.

Ambrosius’s Reign and Stonehenge

From this point on, Ambrosius was the new high king of the Britons. His reign was not a lengthy one, so there are not many events which took place during it.

One of the only other notable events is the construction of a stone monument to memorialize the slain British leaders from the peace conference.

Merlin and Uther were sent by the king to Ireland to recover an existing stone monument, called the Giants’ Dance.

This was then taken to Britain and established by the site of the peace conference (evidently intended to be Stonehenge).

Death of Ambrosius

Near the end of his life, for some reason not revealed in the HRB, Ambrosius was confined to a sickbed. During this time, his brother Uther was entrusted with the care of the kingdom.

Taking advantage of his vulnerable state, the Saxons craftily poisoned him by the hand of a man named Eopa, ending his life. Uther then officially succeeded him as high king of the Britons.

When He Lived

The earliest account of Ambrosius is Gildas’s mention of him. Although this writer did not give an extensive amount of dating information, he did tell us enough to work out the general period in which Ambrosius must have lived.

He tells us that Ambrosius was the military leader who led the Britons against the Saxons before the Battle of Badon was fought (and possibly during that battle too, but see ‘Victor at Badon?’ below).

Saxon Invasion and Ambrosius’s Timeline

The Saxons were brought to Britain in 428 according to the Historia Brittonum. This date is seemingly confirmed by the fifth-century Life of Germanus, which records that the Britons were fighting against the Saxons as early as c. 431.

The Gallic Chronicle of 452 also testifies to the Saxons having gained a considerable amount of British territory by 441.

Ambrosius’s Birth and Vortigern’s Rise to Power

According to later legend, Ambrosius was just a child when Vortigern came to power, which was shortly before the Saxon conquest began. This would indicate that his birth took place in about the first quarter of the fifth century.

More specifically, the Historia Brittonum claims that Vortigern rose to power in 425. If Ambrosius was a child at that time (just ‘a child in his cradle’ according to the HRB), then we can estimate that he was born in about the year 420.

Campaign Against the Saxons and Ambrosius’s Life in Brittany

This estimate accords with the other information about when this commander lived. Bede speaks of him as beginning his campaign against the Saxons in the reign of Zeno, which could mean anywhere from 474 until 491.

Since Ambrosius was (according to the HRB) raised in Brittany and only returned to Britain when he was motivated to stop the Saxons after the massacre of the British leaders, this large gap between 420 and 474 is quite feasible.

Historicity: Was Aurelius Ambrosius Real?

As mentioned before, Gildas wrote about Ambrosius. After referring to the fact that the Saxons savagely wrought destruction to the Britons and sent them fleeing to the mountains and the forests, Gildas tells us this:

“The poor remnants of our nation… took arms under the conduct of Ambrosius Aurelianus, a modest man, who of all the Roman nation was then alone in the confusion of this troubled period by chance left alive.”

St. Gildas

Ambrosius’s Historical Name

As we can see, it appears that the historical name of this leader was actually ‘Ambrosius Aurelianus’ as opposed to ‘Aurelius Ambrosius’.

The form ‘Aurelius Ambrosius’ was used at least as early as Bede, and that is the form that most subsequent sources use.

Historicity of Ambrosius

But the primary point to be taken from the above quote is the fact that Ambrosius was almost certainly a historical figure.

Gildas lived less than a century after the events he describes, and he refers to the living descendants of Ambrosius and comments on their moral character.

So we can be very confident in the historicity of Ambrosius, though we know little about the historical figure.

Ambrosius’s Relationship with Uther Pendragon

Firstly, is it plausible that Ambrosius really was the older brother of Uther?

Significantly, Gildas claims that Ambrosius was ‘of all the Roman nation then alone in this troubled period’.

This would seem to exclude the possibility that he had a brother who was fighting alongside him during that period.

Possible Connections to King Arthur

What about the second matter, that of Ambrosius’s connection to Arthur? Is it reasonable to believe that they really were relatives, as the legends claim?

While it does not seem possible that the former really was the latter’s paternal uncle (for the reasons related to Uther discussed above), there is nothing inherently unlikely about a familial connection of some kind between the two men.

Ambrosius’s Children and Succession

Given that Ambrosius must have had children, it would be wholly logical for one of them to have succeeded to the throne, assuming that Ambrosius really was a king and not just a military commander (he is called ‘the great king among the kings of the Britons’ as early as the Historia Brittonum).

Thus, we would very logically expect a son or grandson of Ambrosius to have been reigning among the Britons in the sixth century, exactly the time in which Arthur was supposed to have been commanding them.

Ambrosius as King Arthur’s Grandfather

We know that Ambrosius had descendants who were still active in Gildas’s time, so the idea that Arthur was actually the son or the grandson of Ambrosius (forming the linking generation between Ambrosius and his descendants in Gildas’s time) is quite an appealing one.

It harmonizes the legend of them being related with the historical information mentioned by Gildas.

So, while the legends do not appear to be perfectly accurate on this point, there is good reason for concluding that there genuinely was a familial relationship between Ambrosius and Arthur.

Although the exact nature of their connection may be debated, the evidence supports the idea of a strong link between these two historically significant figures.

Victor at Badon?

One major question for researchers of this period is: Who really led the Britons to victory at the Battle of Badon?

While this has traditionally been attributed to Arthur, there are a number of scholars who believe that the real victor was Ambrosius. The reason for this is Gildas’s description of the Battle of Badon.

It follows on directly from his description of Ambrosius, as can be seen here:

“[The Britons] took arms under the conduct of Ambrosius Aurelianus, a modest man, who of all the Roman nation was then alone in the confusion of this troubled period by chance left alive. His parents, who for their merit were adorned with the purple, had been slain in these same broils, and now his progeny in these our days, although shamefully degenerated from the worthiness of their ancestors, provoke to battle their cruel conquerors, and by the goodness of our Lord obtain the victory…”

St. Gildas

Ambrosius as the Victor at Badon?

It is understandable why some researchers conclude that Gildas was attributing the battle to Ambrosius. It certainly could mean that.

Under this interpretation, the battle was falsely attributed to Arthur at a later date, or that Ambrosius was the original Arthur that the legends eventually came from.

An Alternative Interpretation

However, is it necessarily the case that Arthur’s greatest victory was not his, but actually Ambrosius’s?

While the words of Gildas allow for that interpretation, it must be emphasised that his words definitely do not make the matter clear.

When he mentions the fact that ‘sometimes the Britons, and sometimes the Saxons’ were victorious until the Battle of Badon, this easily allows for a long period of time in which the Britons (and the Saxons, for that matter) followed various different commanders.

Ambrosius’s Age and the Battle of Badon

There is actually reason to believe that Ambrosius could not have been the victor at Badon. Recall that he was likely born in c. 420.

The Battle of Badon, meanwhile, is generally thought to have occurred in c. 500 or a decade or two later (the Annales Cambriae places it in 516).

If we use the earlier date, this would make Ambrosius 80 years old at the time of the battle. Using the later date of 516 would make Ambrosius nearly 100!

Obviously, if the date of c. 420 for Ambrosius’s birth is correct (and the fact that he fought a battle in 437 strongly suggests that it could not have been any later), then Ambrosius simply cannot have been the victor at Badon.

The Riothamus Theory

A more realistic theory about Ambrosius is that he was identical to Riothamus. This fifth-century historical figure is known to have fought a battle against the Visigoths in Gaul in 470. He lost the battle, although he himself did not perish.

The historian Jordanes described Riothamus as ‘king of the Britons’, though it is debated whether he meant the Britons of Britain or the Britons of Brittany.

Attempts to Identify Riothamus with Arthur

Many people have attempted to identify this historical king with Arthur himself, but the reasons for doing so are very weak and do not stand up to scrutiny (see the article ‘King Arthur‘).

One of the problems is that Riothamus lived too early to have been identical to Arthur. However, he is a perfect chronological match for Ambrosius.

Ambrosius and Riothamus: A Possible Connection

Consider: Ambrosius was supposedly away in Brittany from 425 (when Vortigern took power) until the mid-470s (when he returned to fight against the Saxons). He was allegedly the heir to the throne of Britain, the son of the former high king.

And over in Gaul we have a figure who was potentially the king of Brittany with a name that may actually have been a title meaning ‘Kingliest’ (although some researchers believe that ‘Riothamus’ was a proper name).

The year of 470 for his battle against the Visigoths places him in Gaul in the period in which Ambrosius was there.

The Issue of Riothamus’s Name

So, could Riothamus have actually been Ambrosius? It is certainly a possibility.

It is a much more appealing theory than identifying Riothamus with Arthur.

However, one of the same issues with the Arthur identification also applies here. There is some reason to believe that Riothamus was not a title, but was actually the man’s name. It is used in personal correspondence between him and Sidonius Apollinarius.

The Ambiguity of the Theory

If this is so, then this would appear to disprove the theory that Riothamus was Ambrosius; unless, of course, he was known by more than one name, which is possible.

In truth, the theory has a fairly weak foundation to start with. There are not a whole host of similarities between Riothamus and Ambrosius, but only a few. Nonetheless, this theory remains a distinct possibility, albeit not necessarily a very likely one.

Final Thoughts

In conclusion, Ambrosius was a significant fifth-century figure, likely born around 420 and taken to Brittany for protection.

He possibly returned to Britain to fight Vortigern and later battled the Saxons. Ambrosius’s father should not be identified with Constantine III, but with another man of the same name.

Although not Uther’s brother, he could have been related to Arthur. Various theories about Ambrosius include him being Riothamus or the true victor at Badon, but neither is highly probable.

Ambrosius remains a figure with potential for more theories in the future.

Arthurian Bibliography

See also my ever-expanding list of primary and secondary sources.

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Caleb Howells is a writer from the south coast of England. He has spent years researching various different myths and legends from around the world, with his primary area of interest being the legends of King Arthur. In May 2019, Caleb published King Arthur: The Man Who Conquered Europe, outlining his theories on the origin of the legend.

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