Avalon is a mythical island featured in the Arthurian legend. It first appeared in Geoffrey of Monmouth's 1136 Historia Regum Britanniae as a place of magic where King Arthur's sword Excalibur was made and later where Arthur was taken to recover from being gravely wounded at the Battle of Camlann. Since then, the island has become a symbol of Arthurian mythology, similar to Arthur's castle of Camelot.

Historia regum Britanniae, originally called De gestis Britonum, is a pseudohistorical account of British history, written around 1136 by Geoffrey of Monmouth. It chronicles the lives of the kings of the Britons over the course of two thousand years, beginning with the Trojans founding the British nation and continuing until the Anglo-Saxons assumed control of much of Britain around the 7th century. It is one of the central pieces of the Matter of Britain.