Ronald Brittain MBE MSM (2 September 1899 – 9 January 1981) was a regimental sergeant major (RSM) in the British Army. Reported on widely in the newspapers of the day, he featured in several British military training films during the Second World War. He was said to have possibly the loudest voice in the British Army. On retiring from the army in the 1950s, Brittain's fame enabled him to enjoy a career in advertising, voice-over work and acting, playing characters that resembled an archetypal Sergeant Major.