Diplomatic License Plates are issued by the United States Department of State to approved diplomats. This is an exception to the general rule in the US that license plates are issued by the state, and not the federal, government.

Plates issued to cars based in the District of Columbia follow the pattern of a letter identify the status of the owner, followed by the two-letter county code, followed by a three-digit number. (L LL NNN) Plates issued to cars based at the United Nations in New York, New York are reversed, with the three-digit number first, followed by the two-letter country code, followed by the status code (NNN LL L). This is because representatives of certain countries are limited to travel to certain radii from their base, and the system allows the city of asignment to be identified easily.

The status codes are "C" for Foreign Consul; "D" for Diplomat; "S" for Non-Diplomatic Staff; and "A" for a UN employee. The rights of the driver and car under diplomatic immunity are defined by this status code.

The country codes are, unlike most other country codes, purposefully illogical, not standing for anything. For example, France is "DJ" not "F" and Australia is "XZ" not "AUS". This is to prevent the general public from targeting diplomats from particular countries. However, lists of the codes are available.

It is an, apparently true, urban legend however that the code used for the former USSR of "FC" stood for F---ing Communists, the code system having been devised during the height of the Cold War by Ronald Reagan aide Dana Rohrbacher . Today Russia is assigned code "YR".

Certain US states will issue Honorary Consul plates to US citizens who have been appointed to that ceremonial office. These plates do not confer diplomatic immunity and are not a part of the US State Department system.