The Big Four can refer to:
- Big Four - a secret syndicate of criminals dedicated to world domination.
- The Man who was Number Four - a series of 12 short stories which Agatha Christie published in The Sketch from Jan - Mar 1924 which narrates the efforts of Hercule Poirot against the Big Four syndicate.
- The Big Four - a novelisation of the 12 short stories published in 1927.
- The Big Four (Detective Club Edition) - a short story collection published in 2016 containing the original text of the short stories as published in the Sketch.