A postal code (known in various countries as a post code, postcode, or ZIP code) is a series of letters and/or digits appended to a postal address for the purpose of sorting mail.

Germany was the first country to introduce a postal code system, in 1941. The United Kingdom followed in 1959 and the United States in 1963.

In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems.