The Shadow is a fictional character created by American magazine publishers Street & Smith and writer Walter B. Gibson. Originally created to be a mysterious radio show narrator, and developed into a distinct literary character in 1931 by Gibson, The Shadow has been adapted into other forms of media, including American comic books, comic strips, serials, video games, and at least five feature films. The radio drama included episodes voiced by Orson Welles.The Shadow debuted on July 31, 1930, as the mysterious narrator of the radio program Detective Story Hour, which was developed to boost sales of Street & Smith's monthly pulp Detective Story Magazine.

 When listeners of the program began asking at newsstands for copies of "that Shadow detective magazine", Street & Smith launched a magazine based on the character, and hired Gibson to create a concept to fit the name and voice and to write a story featuring him. The first issue of the pulp series The Shadow Magazine went on sale April 1, 1931.On September 26, 1937, The Shadow, a new radio drama based on the character as created by Gibson for the pulp magazine, premiered with the story "The Death House Rescue", in which The Shadow was characterized as having "the hypnotic power to cloud men's minds so they cannot see him".

In the magazine stories, The Shadow did not become literally invisible.The introductory line from the radio adaptation of The Shadow – "Who knows what evil lurks in the hearts of men? The Shadow knows!" – spoken by actor Frank Readick, has earned a place in the American idiom. These words were accompanied by an ominous laugh and a musical theme, Camille Saint-Saëns' Le Rouet d'Omphale ("Omphale's Spinning Wheel" composed in 1872).