Third Secretary is one of the standard diplomatic ranks recognised under the Vienna Convention on Diplomatic Relations (1961), which in Article 14 classifies heads of mission but leaves subordinate ranks to states' own practice. In most foreign services, the hierarchy of diplomatic staff below the ambassador and Deputy Chief of Mission runs: Minister-Counsellor, Counsellor, First Secretary, Second Secretary, Third Secretary, and Attaché.
A Third Secretary is usually a career diplomat in the early years of an overseas posting, often handling a defined portfolio such as consular affairs, public diplomacy, political reporting on a narrow issue, economic data collection, or administrative coordination. They draft cables, take notes in meetings, liaise with mid-level host-country officials, and support more senior diplomats during negotiations or visits.
Despite the junior title, Third Secretaries enjoy full diplomatic status under Article 37(1) of the Vienna Convention, including inviolability of the person (Article 29) and immunity from the receiving state's criminal jurisdiction (Article 31). Their names appear on the Diplomatic List published by the host foreign ministry, and they are accredited through the standard notification procedure.
Promotion patterns vary: in the U.S. Foreign Service, the equivalent is roughly an FS-04 or FS-05 officer; in the UK's FCDO, a B3-grade officer; and in India's IFS, an officer is typically appointed Third Secretary on first posting abroad after probation. Tours generally last two to four years before rotation.
The rank is sometimes used as cover for intelligence officers, a practice acknowledged in expulsion cases when host governments declare individuals persona non grata under Article 9. However, the overwhelming majority of Third Secretaries are conventional diplomats building expertise for later, more senior assignments.
Example
In 2018, the UK expelled 23 Russian diplomats, several listed as Third Secretaries, following the Salisbury poisoning of Sergei Skripal.