This is a controversial question, but here is my personal opinion. King Arthur was a king of the Britons, a Celtic people, in the fifth and sixth centuries. In the Easter Annals,a document from the dark ages, he is mentioned twice: 516: Battle of Mt. Badon in which Arthur carried the cross of our lord Jesus Christ on his shoulders for three days and nights and the Britons were victorious 537: Strife of Camlan in which Arthur and Medraut fell. Those aren't the exact wordings but fairly close. Badon was crucial point in Arthur's military career because it stopped the Saxons from coming further west for a few decades. It is assumed that Arthur died in Camlan, but it is not really known. Perhaps he survived and retired from public life. Especially since he lost the battle. This could be where the legend of the once and future king comes from. He left Britain to his sucessor, Constantine of Dumnonia. If you are seeking more information about this topic, I highly recommend reading King Arthur: The truth behind the legend by Rodney Castleden. It goes into far more depth than I have. What I have stated is not all the evidence. There is more, but I don't have the time and will to write it all down right now.
Myth,legend
There is no concrete historical evidence that proves King Arthur was a real person. The stories of King Arthur are largely based on myth and legend, with some scholars suggesting that he may have been a composite of multiple historical figures. The lack of reliable contemporary records and the fantastical elements of the Arthurian legend make it difficult to establish the existence of a historical King Arthur.
The myth of King Arthur has always puzzled me.
According to some of the legends, the war between Arthur and his rivals (usurpers), the end of the Knights of the Round Table and the death of Arthur brought about the downfall of the mythical castle, too. The surviving knights left for the Holy Land, Guinevere entered a monastery and so did Lancelot, in certain versions of the myth.
There is no evidence that anyone has been reincarnated, and King Arthur is more myth and legend than fact, so there is no evidence that King Arthur (or anyone else for that matter) has been reincarnated.
It is not known for certain if King Arthur actually lived or is a person of folklore and myth. It is said he came from and ruled England.
A story or myth that has been passed down from person to person over many years. The validity of the story cannot be proven to be correct or not. Such as the Legend of King Arthur.
There is some controversy as to whether there was ever a real King Arthur at all. Some have found reason to believe that castle/fortress remains found in the area near Salisbury suggest a one-time home for the legendary Arthur, but there is insufficient evidence to point to a true home to King Arthur in the history books. He did live in Camelot though, in the fantasy stories inspired by the potentially true character.
Camelot, the legendary castle associated with King Arthur, is believed to have derived its name from the Welsh word "Camelot," which may relate to the term "Camelot" in later romances or stories. Some theories suggest it could be linked to the Latin word "camelus," meaning "camel," referencing the area's geography or local folklore. However, the exact origin of the name remains uncertain and is steeped in myth. Its fame largely comes from medieval literature, particularly the works of Geoffrey of Monmouth and later Arthurian romances.
King Henry was an actual person.
Camelot is often considered perfect due to its representation of an idealized society characterized by chivalry, justice, and noble ideals. It serves as a symbol of Arthurian legend, where King Arthur and his Knights of the Round Table embody virtues such as honor, bravery, and unity. The concept of Camelot captures the aspiration for a harmonious and equitable community, making it a timeless emblem of utopian ideals. Its allure lies in the blend of myth, romance, and moral integrity, appealing to our longing for a better world.
King Arthur or any of the Greek Myths including the Gods like Zeus and Posiedon.