Spiritualism is a religion that began in the United States and flourished from the 1840s to the 1920s—especially, though by no means exclusively—in English-language countries. By 1897, it is said to have had more than eight million followers in the United States and Europe, mostly drawn from the middle and upper classes. The religion's distinguishing feature is the belief that the spirits of the dead can be contacted by "mediums," and can therefore provide living people with information about the afterlife. .

Developing for a half century without canonical texts or formal organization, the religion attained a cohesion through widely distributed periodicals, tours by trance lecturers, camp meetings, and the missionary activities of accomplished mediums. Many of the most prominent Spiritualists were women, and most adherents supported radical causes like abolition and women's suffrage. By the late 1880s the credibility of the movement had weakened, due to widely publicized accusations of fraud, and formal organization began to appear. Spiritualism still exists today, primarily through the form of the Spiritualist Church, though modern organisations have generally rejected more Christian elements and embraced more New Age ideas.