Ronald Brittain, MBE (2 September 1899 – 9 January 1981) was a well-known Regimental Sergeant Major (R.S.M.) in the British Army. The Warrant Officer class 1, who was reported on widely in the newspapers of the day, 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, R.S.M. Brittain's fame enabled him to enjoy a career in advertising, voice-over work and acting, playing characters that resembled an archetypal Sergeant Major.