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.
The television series Secrets of War suggested him as a possible inspiration for Q branch in James Bond.
Fairbairn served with the Royal Marine Light Infantry starting in 1901, and joined the Shanghai Municipal Police (SMP) in 1907. He served in one of the red light districts. During his service with the International Police in Shanghai, Fairbairn reportedly engaged in hundreds of street fights in the course of his duties over a twenty-year career, where he organised and headed a special anti-riot squad. Much of his body, arms, legs, torso, even the palms of his hands, was covered with scars from knife wounds from those fights. Fairbairn later created, organised and trained a special anti-riot squad for the Shanghai police force, as well as developing numerous firearms training courses and items of police equipment, including a special metal-lined bulletproof vest designed to stop high-velocity bullets from the 7.63x25mm Mauser pistol.