Regimental Sergeant Major

Regimental Sergeant Major (RSM) is an appointment held by Warrant Officers Class 1 (WO1) in the British Army, Royal Marines and many Commonwealth armies, and by Chief Warrant Officers (CWO) in the Canadian Forces. Only one WO1/CWO holds the appointment of RSM in a regiment or battalion, making him the senior warrant officer; in a unit with more than one WO1, the RSM is considered to be "first amongst equals". The RSM is primarily responsible for maintaining standards and discipline. In the Household Cavalry he is instead called the Regimental Corporal Major (RCM).

The RSM is never addressed as "Sergeant Major"; he is addressed as "Mr (surname)" by officers, and as "Sir" or "Mr (surname), Sir" by his subordinates. With the exception of the Canadian Forces, only his commanding officer (the Lieutenant-Colonel commanding his battalion or regiment) has the privilege of addressing him as "RSM". Unlike most warrant officers, RSMs wear Sam Brownes instead of sashes.

The same appointment exists in the Australian Army, New Zealand Army and Singapore Armed Forces. In the Singapore Armed Forces, RSMs hold one of four ranks: Second Warrant Officer (2WO), First Warrant Officer (1WO), Master Warrant Officer (MWO), or the most senior warrant rank, Senior Warrant Officer (SWO).

The equivalent rank in the US Army is a Command Sergeant Major.

The billet of Regimental Sergeant Major exists in the United States Marine Corps. In the USMC a Regimental Sergeant Major is the senior enlisted advisor to the Regimental Commander.

Regimental Sergeant Major of the Army

In Australia, the senior warrant officer in the Australian Army holds the unique rank of Warrant Officer (introduced in 1991 and senior to WO1) and the appointment of Regimental Sergeant Major of the Army (RSM-A). This appointment, based on the United States Army's practice of appointing a Sergeant Major of the Army, has existed since January 1983, and was originally held by a WO1. It is the equivalent of the Royal Australian Navy's Warrant Officer of the Navy (WO-N) and the Royal Australian Air Force's Warrant Officer of the Air Force (WOFF-AF).