The United States Postal Service (USPS) is a government owned agency in the United States which is responsible for delivering mail. It is one of the oldest government agencies in America, and it also holds a monopoly on certain aspects of mail delivery. This monopoly is interpreted as part of the Postal Service mission, written into the United States Constitution. Through the United States Postal Service, citizens can send mail and parcels almost anywhere in the world, usually at reasonable prices.

In 1775, the United States Postal Service was established, with Benjamin Franklin as the Postmaster General. Franklin was directed to establish a series of branches, and to set up reliable mail delivery along the Eastern Seaboard. As the nation expanded, so did the United States Post Office, and it is now the third largest employer in the United States, with one of the largest civilian truck fleets in the world.

The status of the Postal Service can be confusing. The organization is entirely owned by the United States Government, but its employees are all civilian. It is managed by a Board of Governors appointed by the President. This board is responsible for setting postal policies, including the price of stamps. Because the United States Postal Service is a government agency, it enjoys certain privileges, such as the right to negotiate diplomatic terms related to the mails directly with other nations, and the monopoly on the nation's mail. All non-urgent first class mail must be sent through the post office, although urgent deliveries can be sent through private carriers and couriers, and packages may be handled by other companies such as the United Parcel Service. The Postal Service is also the only organization which may place material into mailboxes.

In addition to the United States Postal Service itself, there are also two inspection services linked with the post office. The Inspector General is supposed to be responsible for maintaining the integrity of the Postal Service and its mails, and also assembles financial accountability reports and other such documentation. The Postal Inspection Service is a law enforcement agency which monitors mail fraud and threats against the United States Postal Service. Both organizations work to keep the United States mail safe and secure.

Anyone can use the services of the United States Postal Service for the fee of a stamp. Since the organization is government controlled and it has a monopoly on mail delivery, it can keep prices extremely low, making them affordable for all. Citizens can purchase stamps or precise postage in branch offices, also called post offices, and they can drop their mail into any one of millions of postal drop boxes around the United States. The United States Postal Service also offers services like insurance, delivery confirmation, and expedited mail.