A banner of arms is a type of heraldic flag, characterised by sharing its imagery with that of the coat of arms (i.e. the shield of a full heraldic achievement, rendered in a square or rectangular shape of the flag).
The term is derived from the terminology of heraldry but mostly used in vexillology. Examples of modern national flags which are banners of arms are the flags of Austria, Iraq, and Switzerland.
The banner of arms is sometimes simply called a banner, but a banner is in a more strict sense a one of a kind personal flag of a nobleman held in battle.