U.S. Special Delivery was a postal service paid for with additional postage for urgent letters and postal packets which are delivered in less time than by standard or first class mail service. Its meaning is different and separate from express mail delivery service. Essentially it meant that a postal packet was delivered from a post office to the addressee immediately once it arrived at the post office responsible for delivering it, rather than waiting for the next regular delivery to the addressee.

Postal service in the United States began with the delivery of stampless letters whose cost was borne by the receiving person, later encompassed pre-paid letters carried by private mail carriers and provisional post offices, and culminated in a system of universal prepayment that required all letters to bear nationally issued adhesive postage stamps.