"The Cottingley Fairies are a series of five photographs taken by Elsie Wright and Frances Griffiths, two young cousins living in Cottingley, near Bradford in England, depicting the two in various activities with supposed fairies. In 1917, when the first two photos were taken, Elsie was 16 years old and Frances was 10. In 1981 the two women admitted to faking all but one of the photographs, but insisted that they really had seen fairies."
Read more at Wikipedia
And see the rest of the remarkable photos here