"All the Madmen" is a song written by David Bowie in 1970 for the album The Man Who Sold the World, released later that year in the U.S. and in April 1971 in the UK. One of a number of tracks on the album dealing with insanity, it has been described as depicting "a world so bereft of reason that the last sane men are the ones in the asylums".

The track opens with acoustic guitar and recorder, creating an atmosphere that Bowie biographer David Buckley called "childlike dementia", before transforming into a heavy rocker featuring distorted chords from the electric guitar played by Mick Ronson, augmented by Moog synthesizer played by Ralph Mace. Later, Ronson plays melodic lead guitar, before return to heavy riffing and then melodic lead guitar as the song concludes. Coincidentally, in the same year, Ronson played lead guitar on Elton John's recording of "Madman Across The Water".

It ends with the chant "Zane zane zane, ouvre le chien", the latter phrase literally meaning "open the dog" in French.

The production of the song also made use of varispeed vocals, which Bowie had first employed – though only for comic effect – on "The Laughing Gnome" in 1967. Bowie has said that the song was written for and about his half brother, Terry, a schizophrenic and inmate of Cane Hill mental institution (pictured on the original U.S. cover of The Man Who Sold the World) until his suicide in 1985. The lyrics include references to lobotomy, the tranquilliser Librium and EST, or Electroshock Therapy, a controversial treatment for some types of deep depression and mental illnesses.

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