Ruth Shick Montgomery (June 11, 1912 – June 10, 2001) was a self-described Christian psychic in the tradition of Jeane Dixon and Edgar Cayce. She was a biographer of Dixon and a protégée of Arthur Ford who claimed he (like Cayce) could access the Akashic Records (or database) of the Universe.
Montgomery initially believed her mission on Earth was to educate the public on her belief in life after death, which is common among spiritualists. However, she also studied reincarnation and came to believe that mental and physical illnesses often have their origins in past lives.
With other like-minded mystics, Montgomery founded the Association for Past Life Research and Therapy. Her many books (which she says were channelled via Automatic writing from her spirit guides) popularised spiritualist notions in public consciousness in the 1970s through the 1990s, and paved the way for what is now known as New Age religion. Montgomery is particularly noted for her popularization of walk-in theory whereby a person's soul can depart a hurt or anguished body and be replaced with a new soul to take over the body.