Ronald Brittain, MBE MSM (2 September 1899 – 9 January 1981) was well known during his lifetime as an archetypal Regimental Sergeant Major (R.S.M.) and for having possibly the loudest voice in the British Army. He was often featured in World War II training films and was reported on widely in the newspapers of the day. On retirement from the army, R.S.M. Brittain's notoriety enabled him to enjoy a career in advertising, voice over work and film acting, usually playing a Sergeant Major.