Answer:
King Arthur is a legend whose origins are lost in the mists of time. Many of the stories about him and his knights were simply made up by French troubadors during the Middle Ages. Some stories about him bear some resemblance to actual historical events of the 5th through 7th centuries. The ultimate man behind the myth, the historical figure to whose life all later legendmaking was eventually added, may have been a 5th century Romano-British leader known to history as Riothomus. That name however is more likely a title (it means something like Supremely Royal) rather than a personal name. What the man's actual name was is not recorded. It could have been something like Artorius.