An airmail stamp is a postage stamp intended to pay either an airmail fee that is charged in addition to the surface rate, or the full airmail rate, for an item of mail to be transported by air.

A postage stamp is a small piece of paper issued by a post office, postal administration, or other authorized vendors to customers who pay postage. Then the stamp is affixed to the face or address-side of any item of mail—an envelope or other postal cover —which they wish to send. The item is then processed by the postal system, where a postmark or cancellation mark—in modern usage indicating date and point of origin of mailing—is applied to the stamp and its left and right sides to prevent its reuse. Next the item is delivered to its addressee.