This is a list of entities that have issued postage stamps at some point since stamps were introduced in 1840. The list includes any kind of governmental entity or officially approved organisation that has issued distinctive types of stamp for postal purposes. These include post offices in foreign countries and postal services organised by military occupations, international organisations, colonies, provinces, city-states and some revolutionary movements. The list includes members of the Universal Postal Union that are also listed at postal organisations.

Many of these entities are historic and some were very short-lived indeed. Philatelists and stamp collectors often refer to the entities that no longer issue stamps as dead countries.

The dates are the generally agreed-upon dates of first and last stamp issues. "Date of issue" is taken to mean the date when a particular type or variation was first issued but its usage would often continue for many years. For example, although an entity may have issued its last stamp in 1951, actual usage may have continued until 1960: in that case, 1951 is the last stamp issue date.

Besides the period of which stamps were issued in the name of a particular entity, the list under that entity also bears any other name in which stamps had been issued for territory, name of any other entity which had had its stamps used in that territory, or new names which had subsequently replaced the name of that entity, together with their respective periods.