The Avalon Series is a series of fantasy novels written by Marion Zimmer Bradley, with help from Diana L. Paxson. Paxson later took over sole authorship after Bradley's death in 1999. The series focuses on the legendary island of Avalon and the various women who have shaped its history and that of Britain.
The Avalon series retells the Matter of Britain from the point of view of the women behind the throne. Through a set of stories that spans several centuries, it tells of how the mystic isle of Avalon was created, its history, life in Britain under Roman authority, and how Avalon and its ancient traditions faded from the world because of a new religion, Christianity. All stories are told by women who were powerful during their lifetime, such as Eilan, High Priestess of the Forest House, Helena, mother of the Roman Emperor Constantine, and Morgaine, High Priestess of Avalon (later remembered as the sorceress Morgan le Fay).
The series explores the King Arthur story and related legends through a feminist lens, as well as incorporating historical figures and events, elements of Celtic paganism, and contemporary neo-pagan traditions. The ideological conflict of the pagan and Christian characters, as well as the belief that there is wisdom to be found in both traditions, are frequent themes of the series.
The novels are connected via Avalon itself and the implication (strongly hinted at, though rarely outright stated) that several characters throughout the series are the same souls reincarnated.
First established in The Mists of Avalon, the series' version of the legendary island is notably different from other depictions, though it draws from and expands earlier legends. As in Geoffrey of Monmouth, Avalon is ruled by an order of women, explicitly identified by Bradley with the pre-Christian Brythonic religion. Drawing from legends that associate Avalon with the town of Glastonbury in Somerset, England, Bradley establishes her Avalon as a parallel universe of sorts to Glastonbury, co-existing in the same area but accessible only by summoning a magical mist.