Marion Zimmer was born in Albany, New York, on June 3, 1930, and married Robert Alden Bradley in 1949. Mrs. Bradley received her B.A. in 1964 from Hardin Simmons University in Abilene, Texas, then did graduate work at the University of California, Berkeley, from 1965-1967.

She made her first professional sale to Vortex Science Fiction in 1952. She wrote everything from science fiction to Gothics, but is probably best known for her Darkover novels. In addition to her novels, Mrs. Bradley edited many magazines, amateur and professional, including Marion Zimmer Bradley's FANTASY Magazine, which she started in 1988. She also edited an annual anthology called SWORD AND SORCERESS..

Over the years she turned more to fantasy. She wrote a novel of the women in the Arthurian legends—Morgan Le Fay, the Lady of the Lake, and others—entitled THE MISTS OF AVALON, which made the New York Times bestseller list both in hardcover and trade paperback, and she also wrote THE FIREBRAND, a novel about the women of the Trojan War.

She died in Berkeley, California on September 25, 1999, four days after suffering a major heart attack.