Defendu is a combatives system developed by William Fairbairn and Eric Sykes during the 20th century, also referred to as the Close Quarters Combat System.

Combing boxing, wrestling, Savate, Jujutsu, Judo and street fighting, Fairbairn developed his system initially for the Shanghai Municipal Police.

It was later developed further and taught during the period of World War Two, in particular the special operations executives as a crash course system to give them the skills to attack and defend.