A serjeant-at-arms or sergeant-at-arms is an officer appointed by a deliberative body, usually a legislature, to keep order during its meetings. The word "serjeant" is derived from the Latin serviens, which means "servant". Historically, serjeants-at-arms were armed men retained by English lords and monarchs, and the ceremonial maces which they are associated with were originally a type of weapon.

Sergeant (Sgt) is a rank in use by the armed forces of many countries. It is also a police rank in some police services. The alternative spelling, serjeant, is used in The Rifles and other units that draw their heritage from the British light infantry. Its origin is the Latin serviens, 'one who serves', through the Old French term serjant.