Born Marion Eleanor Zimmer on June 3, 1930, she lived on a farm in Albany, New York, and began writing at the age of 17.

[4] Moira's son, RJ Stern, is a college football player who was featured on season 5 of Last Chance U on Netflix.

In 1966, with her brother Paul Edwin Zimmer, she helped found and name the Society for Creative Anachronism and was involved in developing several local groups, some in New York after her move to Staten Island.

[12] Bradley stated that when she was a child she enjoyed reading adventure fantasy authors such as Henry Kuttner, Edmond Hamilton, C.L.

Her first professional publication was a short story "Women Only", which appeared in the second (and final) issue of Vortex Science Fiction in 1953.

Early in her career, writing as Morgan Ives, Miriam Gardner, John Dexter, and Lee Chapman, Bradley produced several works outside the speculative fiction genre, including gay and lesbian pulp fiction novels; I Am a Lesbian was published in 1962.

The Darkover milieu is a science fantasy fictional world, with science fiction as well as fantasy overtones: Darkover is a lost human colony where psi powers developed to an unusual degree, and work like magic, while technology has regressed to a more-or-less medieval stage.

[16] Bradley took an active role in science fiction and fantasy fandom, promoting interaction with professional authors and publishers and making several important contributions to the subculture.

Starting in the late 1940s and continuing in the 1950s and 1960s, she published her own fanzines, including Astra's Tower, Day*Star, and Anything Box.

As a result, the novel remained unpublished and Bradley demanded the cessation of all Darkover fan fiction.

One story, "The Jewel of Arwen" (originally published in a different form in the fanzine I Palantir #2, August 1961), appeared in her professional anthology The Best of Marion Zimmer Bradley (1985), but was dropped from later reprints.

[19] Bradley was the editor of the long-running Sword and Sorceress anthology series, which encouraged submissions of fantasy stories featuring original and non-traditional heroines from young and upcoming authors.

[20] Her most famous single novel may be The Mists of Avalon,[21] a retelling of the Camelot legend from the point of view of Morgaine and Gwenhwyfar.

In an email to The Guardian, Greyland said that she had not spoken out before because "I thought that my mother's fans would be angry with me for saying anything against someone who had championed women's rights and made so many of them feel differently about themselves and their lives.

[26][27][28] In December 2017, Bradley's daughter published a detailed biography of her mother, including her pedophilia and sexual abuse, in a book entitled The Last Closet: The Dark Side of Avalon.

[31] Janni Lee Simner donated advances and royalties from her two Darkover short stories and, at the request of her husband, Larry Hammer, payment for his sale to Bradley's magazine, to the American anti-sexual assault organization Rape, Abuse & Incest National Network.

[7] In the late 1950s or early 1960s, Bradley and Walter H. Breen founded the Aquarian Order of the Restoration based on the work of Dion Fortune.

Bradley renovated her garage to provide a meeting room for Darkmoon Circle as well as for other local Pagan groups.

As Elfrieda or Elfrida Rivers, she contributed at least to the underground newspaper The East Village Other, the neo-Pagan periodical Green Egg and also Sybil Leek's Astrology Journal, where she wrote horoscopes and book reviews and had her own column as well as occasionally worked as editors with her husband Walter Breen.