William Ewart Fairbairn (28 February 1885–20 June 1960) was a British soldier, police officer and exponent of hand-to-hand combat method, the close combat, for the Shanghai Police between the world wars, and allied special forces in World War II. He developed his own fighting system known as Defendu, as well as other weapons tactics. Notably, this included innovative pistol shooting techniques and the development of the Fairbairn-Sykes Fighting Knife.

William Ewart Fairbairn, född 1885, död 1960, var en brittisk militär och polis som utvecklade en egen närstridsmetod, Defendu. William Ewart Fairbairn är också nämnd som en möjlig förebild till James Bond.