Eelco Nicolaas van Kleffens (17 November 1894 – 17 June 1983) was a Dutch politician and diplomat.

After receiving a Doctor of Laws degree from Leiden University, van Kleffens worked in the Secretariat of the League of Nations.

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.

In 1954 van Kleffens was appointed to the position of President of the United Nations General Assembly for that body's ninth session.