Bath would have been a singularly important place in Arthurian times, not just for Somerset, but for the whole country. Before that, this ancient town had been a centre for Romano-British. Later, it became central to the Saxon kings, who came several centuries after Arthur. Perhaps, the Battle of Badon should be seen as Arthur's attempt to protect Bath from the invaders.

Geoffrey of Monmouth, in his Historia Regum Britanniae, identifies Badon with Bath. And this link has been supported by Professor Leslie Alcock and, more recently, by the Burkitts on both archaeological and philological grounds. However, it must be said that a lot of historians cite several other high hillfort-like places throughout primarily the South of England with the name Badbury as possible locations for the battle.

Bath is the possible site for King Arthur's last great battle, known as the Battle of Badon. There are two interesting and interrelated questions we might consider. Did Arthur himself fight and win a glorious victory at Badon and was this famous battle near our modern day town of Bath?

Depending upon whose view point you take, either this famous battle is one of the only historical events which can be linked to Arthur with a fair degree of certainty or to others this link is based upon spurious historical foundations.

The Battle of Mount Badon was fought some time between AD 490 and 516 (depending on which source you believe). It is important to us because the Saxon invaders were defeated and forced to come to terms with the British. Today, we do not know exactly where Mount Badon was, though it is most likely to have been Little Solsbury hill, above Bath. It would have been called Badon (pronounced 'Bath-on') by the British.

The only contemporary reference comes from Gildas, a Welsh monk who preached a blood and thunder sermon about The Ruin of Britain (Book 1. 25-26) some time before 547. He wrote:

After a time, when the cruel plunderers had gone home, God gave strength to the survivors ... Their leader was Ambrosius Aurelianus, a gentleman who, perhaps alone of the Romans, had survived the shock of this storm: certainly his parents, who had worn the purple, were slain in it ... Under him our people regained their strength and challenged the victors in battle. The Lord assented and the battle went their way.

From then on victory went now to our countrymen, now to their enemies ... This lasted right up till the year of the siege of Badon Hill, pretty well the last defeat of the villains and certainly not the least. That was the year of my birth; as I know, one month of the forty-fourth year since then has already passed.

Gildas' account implies that Badon was won not by Arthur, but by Ambrosius. Arthur is never mentioned in Gildas. However, by the ninth century, Badon had been firmly established as one of Arthur's victories. How had this happened? To find out we must go back to another early writer called Nennius. Nennius mentions Arthur in The History of the Britons (Historia Brittonum IV.56), where it claims that he won the battle of Mount Badon:

At that time the English increased their numbers and grew in Britain … Then Arthur fought against them in those days, together with the kings of the British; but he was their warleader (or 'dux bellorum').

... The twelfth battle was on Badon Hill, in which 960 men fell in one day from a single charge of Arthur's, and no one laid them low save he alone; and he was victorious in all his campaigns.

For more details about the historical accuracy of these sources and other relating to Arthur's battles, please go to Arthur's Battles.

Archaeological evidence shows that the site of the Roman Baths' main spring was treated as a shrine by the Celts, and was dedicated to the goddess Sulis, whom the Romans identified with Minerva; however, the name Sulis continued to be used after the Roman invasion, leading to the town's Roman name of Aquae Sulis (literally, "the waters of Sulis"). Messages to her scratched onto metal, known as curse tablets, have been recovered from the Sacred Spring by archaeologists. These curse tablets were written in Latin, and usually laid curses on people by whom the writer felt they had been wronged. For example, if a citizen had his clothes stolen at the baths, he would write a curse, naming the suspects, on a tablet to be read by the Goddess Sulis Minerva.

The temple was constructed in 60–70 AD and the bathing complex was gradually built up over the next 300 years. During the Roman occupation of Britain, and possibly on the instructions of Emperor Claudius, engineers drove oak piles into the mud to provide a stable foundation and surrounded the spring with an irregular stone chamber lined with lead. In the 2nd century, the spring was enclosed within a wooden barrel-vaulted building, which housed the calidarium (hot bath), tepidarium (warm bath), and frigidarium (cold bath). The city was given defensive walls, probably in the 3rd century. After the Roman withdrawal in the first decade of the 5th century, the baths fell into disrepair and were eventually lost due to silting up.

Post-Roman and Saxon
The Nävelsjö runestone commemorating a Viking who died in Bath.Bath may have been the site of the Battle of Mons Badonicus (c. 500 AD), where King Arthur is said to have defeated the Saxons, although this is disputed. The Anglo-Saxon Chronicle mentions Bath falling to the West Saxons in 577 after the Battle of Deorham. The Anglo-Saxons called the town Baðum, Baðan or Baðon, meaning "at the baths," and this was the source of the present name. In 675, Osric, King of the Hwicce, set up a monastic house at Bath, probably using the walled area as its precinct. King Offa of Mercia gained control of this monastery in 781 and rebuilt the church, which was dedicated to St. Peter. By the 9th century the old Roman street pattern had been lost and Bath had become a royal possession, with King Alfred laying out the town afresh, leaving its south-eastern quadrant as the abbey precinct. Edgar of England was crowned king of England in Bath Abbey in 973.

Norman, Medieval and Tudor
King William Rufus granted the city to a royal physician, John of Tours, who became Bishop of Wells and Abbot of Bath in 1088. It was papal policy for bishops to move to more urban seats, and he translated his own from Wells to Bath. He planned and began a much larger church as his cathedral, to which was attached a priory, with the bishop's palace beside it. New baths were built around the three springs. However, later bishops returned the episcopal seat to Wells, while retaining the name of Bath in their title as the Bishop of Bath and Wells.

By the 15th century, Bath's abbey church was badly dilapidated and in need of repairs. Oliver King, Bishop of Bath and Wells, decided in 1500 to rebuild it on a smaller scale. The new church was completed just a few years before Bath Priory was dissolved in 1539 by Henry VIII. The abbey church was allowed to become derelict before being restored as the city's parish church in the Elizabethan period, when the city experienced a revival as a spa. The baths were improved and the city began to attract the aristocracy. Bath was granted city status by Royal Charter by Queen Elizabeth I in 1590.