Is there some evidence that King Arthur may have been Celtic chieftain?

Yes, some scholars suggest that King Arthur may have been based on a historical Celtic chieftain. Arthur is often depicted as a leader fighting against Saxon invaders in post-Roman Britain, which aligns with the activities of various Celtic leaders during that time. Historical texts, such as the "Historia Brittonum," mention a figure named Arthur who led battles, further fueling the idea that he may have been a real chieftain whose legend evolved over time. However, definitive evidence remains elusive, and much of the Arthurian narrative blends history with myth.