Hereward Carrington (17 October 1880 – 26 December 1958) was an American investigator of psychic phenomena and author. His subjects included several of the most high-profile cases of apparent psychic ability of his times, and he wrote over 100 books on subjects including the paranormal and psychical research, conjuring and stage magic, and alternative medicine. Carrington promoted fruitarianism and held pseudoscientific views about dieting.

Carrington was born in St Helier, Jersey in 1880. He emigrated to the United States in 1888 (although it is a common misconception he emigrated in 1899). Hereward lived with his brother Hedley in Minnesota and appears in the 1900 census there. He settled in New York City in 1904. There he first worked as an assistant editor for Street and Smith magazines. Initially a sceptic about psychic abilities, his interest grew from reading books on the subject and at the age of 19 he joined the Society for Psychical Research (SPR).

Carrington became a member of the American Society for Psychical Research in 1907 and worked as an assistant to James Hyslop until 1908, during which time he established his reputation as an ASPR investigator. However his connection with the ASPR ceased due to lack of funds.

An important early case Carrington investigated and described was that of the medium Eusapia Palladino in 1908. Carrington and two companions went to Naples to see her on behalf of the English SPR, an experience which strengthened his belief in the reality of psychic phenomena. He described her in his 1909 book Eusapia Palladino and Her Phenomena, invited her to the US and helped arrange a tour for her. He detected her cheating at sittings, but also claimed she had genuine supernatural ability. He also made a detailed enquiry into the case of Esther Cox (the Great Amherst Mystery) in 1910. The events surrounding Cox had occurred more than thirty years previously, but Carrington contacted surviving witnesses for statements and published a detailed account of the Amherst phenomena.

Carrington was an amateur conjuror and was critical towards some paranormal phenomena. Carrington in his book The Physical Phenomena of Spiritualism (1907) exposed the tricks of fraudulent mediums such as those used in slate-writing, table-turning, trumpet mediumship, materializations, sealed-letter reading and spirit photography. The book revealed the tricks of mediums such as Henry Slade and William Eglinton. He wrote in the book that after his investigations and studies into the subject of mediumship that 98% of both the physical and mental phenomena were fraudulent. He did however believe that some mediumship phenomena was genuine.

Science historian Sherrie Lynne Lyons wrote that the glowing or light-emitting hands in séances could easily be explained by the rubbing of oil of phosphorus on the hands. In 1909 an article was published in The New York Times titled Paladino Used Phoshorus. Carrington confessed to having painted Palladino's arm with phosphorescent paint, however he claimed to have used the paint to track the movement of her arm, to detect fraud. There was publicity over the incident and Carrington claimed his comments had been misquoted by newspapers.

Carrington exposed the sleight of hand tricks the Eddy Brothers used in an article in the Popular Science magazine. He wrote an introduction to the book Spiritism and Psychology (1911) by Théodore Flournoy which took a psychological approach to cases of mediumship. Carrington gained his PhD in 1918 from Oskaloosa College.

In 1930, he stated "I have no particular theory to defend, and no belief to uphold. I am not a convinced spiritualist; at the same time, I am willing to grant that the evidence for survival is remarkably strong." Among other researches he made a detailed study of the medium Eileen J. Garrett. Carrington's 1957 book The Case for Psychic Survival is devoted to Garrett.