King Arthur and Beowulf are both kings and heroes whose stories originated in England. While there are many differences in their tales, both kings share similarities.
King Arthur and Beowulf are both kings attempting to create a perfect kingdom. Both men are highly revered and considered godlike. Beowulf was said to be the mightiest man on Earth and there was no one else like him. King Arthur was also seen as more than just a man and was thought to have dropped from heaven.
There are mythical aspects in each universe, and both King Arthur and Beowulf embark on a quest to destroy a monster. Beowulf is on a quest to kill Grendel, a demon who haunts the marches and hunts down people. In King Arthur's tale, Arthur is on a quest to Cameliard to kill the beast that lives in the forest surrounding the court.
Arthur and Beowulf are both kings whose tales end tragically and both are determined to die in battle with their comrades. Beowulf meets his demise during a fight with a dragon, after being abandoned in battle by 11 out of the 12 men he took with him. King Arthur is similarly betrayed by one of his own men, a knight of the Round Table, Sir Lancelot. While pursuing Lancelot, Arthur loses his throne to Mordred. Arthur is killed by Mordred during the battle for the throne.