Commandant is a military or police title or rank and can mean any of the following:

• The commander of certain military corps and services, such as the Commandant of the Marine Corps and the Commandant of the Coast Guard in the United States or the Commandant of the (now obsolete) Women's Royal Naval Service in the United Kingdom.
• The commander of a military or police training installation such as a military academy or police academy .
• In some military organisations, the commander of a headquarters unit.
• The commander of a military prison or similar penal installation, such as a concentration camp.
• In some armies and police forces, including the French Army and French National Police, a rank synonymous with major.
• In the British Army, between 1922 and 1928, a Colonel-Commandant was an appointment held by senior colonels, later replaced by the rank of Brigadier.
• In the British Army, the Colonel-Commandant is the honorary commander of some corps, usually a member of the Royal Family or a senior or retired general.