| Honorific-Prefix: | His Excellency |
| Eelco van Kleffens | |
| Office: | Permanent Representative of the Netherlands to the ECSC |
| Term Start: | 1 May 1958 |
| Term End: | 10 December 1967 |
| Predecessor: | Unknown |
| Successor: | Unknown |
| Office1: | Permanent Representative of the Netherlands to NATO and the OECD |
| Term Start1: | 1 December 1956 |
| Term End1: | 1 May 1958 |
| Predecessor1: | Unknown |
| Successor1: | Unknown |
| Office2: | President of the United Nations General Assembly |
| Term Start2: | 1 January 1954 |
| Term End2: | 31 December 1954 |
| Predecessor2: | Vijaya Lakshmi Pandit |
| Successor2: | José Maza Fernández |
| Office3: | Ambassador of the Netherlands to Portugal |
| Term Start3: | 1 January 1950 |
| Term End3: | 1 May 1958 |
| Predecessor3: | Unknown |
| Successor3: | Unknown |
| Office4: | Ambassador of the Netherlands to the United States |
| Term Start4: | 1 July 1947 |
| Term End4: | 1 December 1956 |
| Predecessor4: | Unknown |
| Successor4: | Unknown |
| Office5: | Permanent Representative of the Netherlands to the United Nations |
| Term Start5: | 17 January 1946 |
| Term End5: | 1 December 1956 |
| Predecessor5: | Office established |
| Successor5: | Unknown |
| Office6: | Minister for United Nations Affairs |
| Term Start6: | 1 March 1946 |
| Term End6: | 1 July 1947 |
| Primeminister6: | Willem Schermerhorn (1946) Louis Beel (1946–1947) |
| Predecessor6: | Herman van Roijen |
| Successor6: | Joseph Luns (1952) |
| Office7: | Minister of Foreign Affairs |
| Term Start7: | 10 August 1939 |
| Term End7: | 1 March 1946 |
| Predecessor7: | Jacob Adriaan Patijn |
| Successor7: | Herman van Roijen |
| Birthname: | Eelco Nicolaas van Kleffens |
| Birth Date: | 1894 11, df=y |
| Birth Place: | Heerenveen, Netherlands |
| Death Place: | Almoçageme, Portugal |
| Alma Mater: | Leiden University (Bachelor of Laws, Master of Laws) Erasmus University Rotterdam (Bachelor of Economics) |
| Occupation: | Politician · Diplomat · Civil servant · Jurist |
Eelco Nicolaas van Kleffens (17 November 1894 – 17 June 1983) was a Dutch politician and diplomat.
Eelco van Kleffens descended from an old Frisian family of public servants. He was the son of Henricus Cato and Jeannette Frésine (Veenhoven) van Kleffens. His younger brother Adrianus van Kleffens would later become a judge at the European Court of Justice. He married Margaret Helen Horstmann on 4 April 1935.
After receiving a Doctor of Laws degree from Leiden University, van Kleffens worked in the Secretariat of the League of Nations. He became secretary to the Directorate of Royal Dutch Petroleum Co. in 1920. He was appointed Assistant Director of the Legal Section of the Netherlands Ministry of Foreign Affairs in 1922 and of the Diplomatic Section in 1927, becoming Director of the latter in 1929. In the early 1930s he was also Secretary-General of The Hague Academy of International Law.
Van Kleffens was appointed the Minister of Foreign Affairs in 1939, weeks before World War II began, and was part of the Dutch government in exile over that period. During the war he penned an account of the German invasion named Juggernaut over Holland which was circulated within the occupied territory, and he was also one of the original signatories of the Benelux union.
Van Kleffens held the position of foreign minister until the Schermerhorn–Drees cabinet of 1946. Following his resignation from the ministerial position (but not from the cabinet) van Kleffens became the Netherlands' representative on the United Nations Security Council, and in 1947 was appointed the ambassador to the United States. In 1950 he became the ambassador to Portugal, and was bestowed the title of Minister of State, a prestigious honour.
In 1954 van Kleffens was appointed to the position of President of the United Nations General Assembly for that body's ninth session.
Van Kleffens was the Dutch representative at NATO and the Organisation for Economic Co-operation and Development from 1956 to 1958, and at the European Coal and Steel Community from 1958 until 1967, after which Van Kleffens retired to Portugal, where he died on 17 June 1983.
| Honours | |||||
| Ribbon bar | Honour | Country | Date | Comment | |
|---|---|---|---|---|---|
| Grand Officer of the Legion of Honour | France | 12 February 1948 | |||
| Knight Grand Cross of the Order of Orange-Nassau | Netherlands | 30 April 1949 | Elevated from Grand Officer (1 March 1946) | ||
| Grand Cross of the Order of Merit | Portugal | 1 October 1954 | |||
| Commander of the Order of the Netherlands Lion | Netherlands | 1 May 1958 | Elevated from Knight (15 July 1931) | ||
| Honorific Titles | |||||
| Ribbon bar | Honour | Country | Date | Comment | |
| Minister of State | Netherlands | 4 July 1950 | Style of Excellency | ||
|-