A Serjeant at Arms (also spelt Sergeant at Arms, and sometimes Serjeant-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."

The office originated in Medieval England; the original responsibilities of the Serjeant at Arms included "collecting loans and , impressing men and ships, serving on local administration and in all sorts of ways interfering with local administration and justice." [1] (http://www.aph.gov.au/house/dept/saa.htm) Circa 1415, the British House of Commons appointed its first Serjeant at Arms.

In the United Kingdom, the Serjeant at Arms serves the Speaker of the House of Commons as well as the whole house. He is responsible for maintaining security, law and order within the precincts of Parliament. The Serjeant at Arms' symbol of office is the ceremonial mace, which functions as a symbol of the Royal authority under which the House of Commons sits. Traditionally, the Serjeant at Arms carries the Mace into the House each day as he leads the Speaker's Procession. No parliament may proceed until the mace is set in its place.

In the House of Lords, the Gentleman Usher of the Black Rod is the Serjeant at Arms.

Many legislatures, including the Commonwealth Realm's member Parliament of Canada, have adopted the British practice of appointing Serjeants at Arms.

The United States Congress has also adopted this tradition.