Spirit photography was a genre of photography popular in the second half of the nineteenth century and early twentieth century in which the photographic process allegedly revealed the presence of "spirits" or ghosts, frequently of departed family members. These photographs—accounts of which circulated widely in the Spiritualist press—were considered in Spiritualist circles to be documentary evidence proving the ability of spirits to communicate with the living; there was also a contemporary countermovement interested in exposing the photographs as fraudulent. The genre also includes photographs from séances and photographs of ghosts captured "spontaneously" at haunted buildings (as opposed to posed portraits from the studio).

Spirit photography grew out of the context of Spiritualism, a utopian religious movement which began in the late 1840s with the ghostly "rappings" heard by the Fox sisters in upstate New York and bolstered by the theological underpinnings of Emanuel Swedenborg via the writings of Andrew Jackson Davis. The core belief of Spiritualism is the ability for the living to communicate with the dead, who, because they are in heaven, can offer moral and ethical guidance to those still on Earth. In Spiritualism's early formulations, mediums—who were usually women—facilitated this communication between the living and the dead, who bore messages of hope and progress. By the late nineteenth century, however, with the influence of Theosophy and occultism, the focus shifted to a darker and more spectacular conception of spirit communication, with a greater emphasis on ghostly materializations, levitations and telekinesis, and ectoplasmic excretions.

Spirit photography should also be understood in the context of the new and rapidly improving technology of photography in the nineteenth century. Many prominent Spiritualists understood themselves to be conducting scientific experiments, and the camera was widely considered to be a neutral and empirical scientific instrument capable of capturing phenomena normally invisible to the human eye. For believers, just as Muybridge's 1878 series "The Horse in Motion" settled the scientific debate about horses' gait, Mumler's 1862 spirit photographs proved the existence of life after death. For skeptics, the use of such an allegedly empirical technology for deception and fraud was an affront against rationalism.

William H. Mumler is frequently credited as the first spirit photographer. Mumler's account of his first spirit photograph (a self-portrait that, after developing, revealed the spirit of his cousin who had died 12 years previously) was published in Andrew Jackson Davis's Herald of Progress in 1862. Mumler is especially well-known for his portrait of the spirit of Abraham Lincoln resting his hands on the shoulders of Mary Todd Lincoln; spirit photography's popularity in the American context is often attributed to the extreme loss of life and culture of mourning during and after the Civil War. Spirit photography spread to Europe in the 1870s, with Frederick Hudson as the first spirit photographer in the United Kingdom and Édouard Isidore Buguet the first in France. Several prominent spirit photographers were subject to debunkings or even charged with fraud, including Buguet, who confessed to double-exposing his plates and was sentenced to a year's jail time, and Mumler, whose case was dismissed because the prosecution could not prove how his photographs had been faked. Photographs of spirits can be created through methods including double exposure, long exposure, or pre-marking glass plate negatives which were then switched through sleight of hand.