A diplomat (from Ancient Greek: δίπλωμα; romanized diploma) is a person appointed by a state or an intergovernmental institution such as the United Nations or the European Union to conduct diplomacy with one or more other states or international organizations.

The main functions of diplomats are: representation and protection of the interests and nationals of the sending state; initiation and facilitation of strategic agreements; treaties and conventions; promotion of information; trade and commerce; technology; and friendly relations. Seasoned diplomats of international repute are used in international organizations (for example, the United Nations, the world's largest diplomatic forum) as well as multinational companies for their experience in management and negotiating skills. Diplomats are members of foreign services and diplomatic corps of various nations of the world.

The sending state is required to get the consent of the receiving state for a person proposed to serve in key diplomatic positions such as an ambassador, also referred to as the head of the mission. The receiving state of the proposed diplomat may accept the diplomat or refuse to accept the diplomat without having to provide reasons for its refusal or acceptance of the person. While the head of the mission or any member of the diplomatic staff is already on duty in the receiving state, the receiving state may still decide at anytime that the person is no longer wanted in the state and is considered persona non grata. When this happens, the sending state may discharge the person.

Diplomats are the oldest form of any of the foreign policy institutions of a state, predating by centuries foreign ministers and ministerial offices. They usually have diplomatic immunity, and in their official travels they usually use a diplomatic passport or, for UN officials, a United Nations laissez-passer.