Spiritualism is a religion in which contact with the spirits of the dead through a medium is central. Spiritualism in its modern incarnation started in the mid-nineteenth century in the United States and essentially grew out of Christianity. It is still perceived as largely Christian in its broadest sense (although no one, least of all Spiritualists, would begin to claim that its beliefs were orthodox), but there are people from other traditions who happily take the title "Spiritualist" whose background is anything but Christian.
See also: