The diplomatic corps or corps diplomatique is the collective body of foreign diplomats accredited to a particular country or body.
The diplomatic corps may, in certain contexts, refer to the collection of accredited heads of mission (ambassadors, high commissioners, and others) who represent their countries in another state or country. As a body, they usually only assemble to attend state functions like a coronation, inauguration, national day or State Opening of Parliament, depending on local custom. They may also assemble in the royal or presidential palace to give their own head of state's New Year greeting to the head of state of the country in which they are based.
The term is sometimes confused with the collective body of diplomats from a particular country—the proper term for which is diplomatic service or foreign service. The diplomatic corps is not always given any formal recognition by its host country, but can be referenced by official orders of precedence.
In many countries, and especially in Africa, the heads and the foreign members of the country offices of major international organizations (United Nations agencies, the European Union, the International Committee of the Red Cross, agencies of the African Union, etc.) are considered members—and granted the rights and privileges—of the diplomatic corps.
Diplomatic vehicles in most countries have distinctive license plates, often with the prefix or suffix CD, the abbreviation for the French corps diplomatique.
Dean of the Diplomatic Corps 
In some countries, the longest-serving ambassador to a country is given the title Dean, or Doyen, of the Diplomatic Corps and is sometimes accorded a high position in the order of precedence. In New Zealand, for example, the dean takes precedence over figures such as the deputy prime minister, former governors-general, and the chief justice. The diplomatic corps may also cooperate amongst itself on a number of matters, including certain dealings with the host government.
Article 4 of the protocol of June 9, 1815, of the Congress of Vienna provided that the apostolic nuncio (often referred to as the papal nuncio) would be dean of the diplomatic corps in the country of appointment. In many countries that have Roman Catholicism as the official or main religion, the nuncio still holds the decanate and is the corps' spokesman on formal occasions. The nuncio to the Philippines still holds this rank out of custom despite the predominantly Catholic country having no official religion. In other cases, the nuncio is treated as the ambassador of the Holy See and has no special precedence.
In practical terms, the Dean of the Diplomatic Corps may have a role to play in negotiating with local authorities regarding the application of aspects of the Vienna Convention on Diplomatic Relations and diplomatic immunity, such as the payment of certain fees or taxes, since the receiving country is required "not to discriminate between states". In this sense, the dean has the role of representing the entire diplomatic corps for matters that affect the corps as a whole, although this function is rarely formalized.
See also