Arthur's sword, symbol of divine kingship, is as much a character in the legend as any human or supernatural being. Excalibur is a symbol of the responsibility of power. In Tennyson's Idylls of the King, one side of Arthur's sword is engraved " in the oldest tongue of all this world,/ 'Take me, but turn the blade and ye shall see,/And written in the speech ye speak yourself,/'Cast me away!'" Tennyson describes Arthur's face as sad as he receives the sword, though Merlin counsels, "'Take thou and strike! the time to cast away/Is yet far-off.'" From the very words etched on the sword, we immediately see the cyclical nature of kingship. "Take me" becomes a call-to-arms for Arthur. By grasping the sword, Arthur accepts responsibility that leadership entails, his sadness an acknowledgement that his power will inevitably wane.

According to legend, Arthur also possessed a lance, Ron, and a shield, Pridwen, on the back of which was painted a portrait of the Virgin Mary. The origins of the sword date back to Celtic mythology, but are found in British, Welsh, and Irish epics. The Welsh name for the sword was Caledvwlch. Irish stories call it Caladbolg, the fairy sword of the hero Cuchulain. In various British Arthur stories, Excalibur is often referred to as "Caliburn." Loomis comments the "ex-" or "es-" prefix that was later added was a "peculiar tendency" of the time period (424).

There are two explanations of the way in which Arthur acquires Excalibur. Contemporary story-tellers are fond of "the sword in the stone" narrative in which young Arthur pulls the magical sword from a rock and anvil bearing this inscription: "Whoso pulleth out this sword of this stone and anvil is likewise King of all England." This is, for example, the main dramatic action in Disney's Sword in the Stone. Arthur's ability to pull the sword from the stone proves his worthiness as King. A second version describes Arthur and Merlin riding to a lake. Here they "see an arm clothed in white samite, rising from the water and holding a sword. Presently a damsel rides rapidly toward them, and at Merlin's bidding dismounts and walks with dry feet over the water. She takes the sword, the arm vanishes,and the damsel brings the coveted weapon back to Arthur. " Here we see the commingling of Christian and pagan motifs, the Christ-like walking on water with the fairy quality of Excalibur and the mythic making of a King.

This version of the story is spoofed in Monty Python and the Holy Grail (1975) when the peasant Dennis, working on a Marxist commune, meets King Arthur. His companion, a warty old woman, asks Arthur how he came to be king, and Arthur, looking skyward, says he received kingship through the supernatural sanction of "the Lady of the Lake, her arm clad in shining samite" who lifted Excalibur "aloft from the bosom of the lake" to bestow it upon him, this description setting up Dennis's rejoinder: "Strange women lying in ponds distributing swords is no basis for a system of government. You can't expect to wield supreme power just because some watery tart threw a sword at you!"