Avalon is a legendary island somewhere in the British Isles.

It is sometimes referred to as the legendary location where Jesus visited the British Isles with Joseph of Arimathea and that it was later the site of the first church in Britain. This location of the Isle of Avalon is usually associated with present day Glastonbury.

It is also said to be the place where the body of King Arthur is buried. He was supposedly brought there via boat by his half sister, Morgan le Fay. According to some legends Arthur merely sleeps there, to awaken at some future time.

According to one theory the word is an anglicisation of the Celtic "Annwyn", the realm of fairies, or netherworld. Geoffrey of Monmouth interpreted the name as the "isle of apples". It would tend to be highly probable, given the fact that apple is still Aval in Breton and Cornish and Afal in Welsh, which pronounces the single f more as a v, and such an extreme corruption is itself highly doubtful.

As early at least as the beginning of the 11th century the tradition that Arthur was buried at Glastonbury Tor appears to have taken shape. Before the surrounding fenland in the Somerset Levels was drained, Glastonbury's high round bulk rose out of the water-meadows like an island. In the reign of Henry II, according to the chronicler Giraldus of Cambrai and others, the abbot Henry de Blois commissioned a search, apparently discovering at the depth of 16 feet a massive oak trunk with an inscription Hic jacet sepultus inclitus rex Arthurus in insula Avalonia. The remains were reinterred with great ceremony, attended by King Edward I and his queen, before the High Altar at Glastonbury Abbey, where they were the focus of pilgrimages until the Reformation.

A nearby valley is named the Vale of Avalon .

However, the Glastonbury legend has frequently been perceived as a fraud due, among other things, to the perceived anachronistic inscription which would have been more fitting to the 10th century than the 6th, the lack of any mention of said discovery in the 10th century, which would not have gone unheard of, added to possible ulterior motives from the abbey. Other theories point to Ile Aval, on the coast of Brittany, and Burgh-by-Sands, in Cumberland, which was in Roman times the fort of Aballava on Hadrian's Wall, and near Camboglanna, upwards on the Eden, now Castlesteads. Coincidentally, the last battle site of Arthur's campaigns is said to have been named Camlann.

In the animated television series, Gargoyles, Avalon plays an important role in the series. It is located in another reality whose rate of time is 1/24th that of Earth that can be accessed when traveling by water and using magic on route to summon the Mists of Avalon. The Princess Catherine, The Magus and Tom flee there along with the surviving Gargoyle eggs from Castle Wyvern. Once there, the humans raise the hatched Gargoyles which grow into adulthood. In the 1990s, the immigrants are twice assaulted by Children of Oberon until the returning Lord Oberon himself is persuaded to let them stay as his honor guard.

In addition, Avalon seems to have an intelligence of its own with altruistic interests that sometimes conflict even with Oberon himself. This is evident when Goliath, his daughter Angela, Eliza Maza and Bronx attempt to leave the island after saving from the first attack. Instead of being sent immediately home to Manhattan, they are sent to various locations around the world to do good deeds and awaken heroes and gargoyle clans to their duties.