The Man Who Knew Too Much

The Man Who Knew Too Much is the title of:

• a 1922 book of detective stories by G. K. Chesterton
• two suspense films directed by Alfred Hitchcock:
  • The Man Who Knew Too Much (1934 film), starring Leslie Banks and Edna Best
  • The Man Who Knew Too Much (1956 film), starring James Stewart and Doris Day
• "The Man Who Knew Too Much" (article), an influential article by Marie Brenner for Vanity Fair on tobacco industry whistle-blower Jeffrey Wigand which formed the basis of the film The Insider
• , a book by David Leavitt

You might also be thinking of:

• "The Man That Knew Too Much", a song by silverchair from their Young Modern album