German diplomat who represented his country in London and Cairo and, as ambassador, in Washington, D.C. (1908–17).

The son of the Prussian diplomat Count Albrecht von Bernstorff, he entered the diplomatic service in 1899, was secretary of legation successively at Belgrade, Dresden, St. Petersburg, and Munich, and (1902–06) was councillor of the embassy in London. He then went as consul-general to Cairo, whence he proceeded as German ambassador in 1908 to Washington, D.C., where he remained until America's declaration of war against Germany in April 1917. During World War I he made great efforts to facilitate mediation of that conflict by President Woodrow Wilson, but he did not receive the support he expected from authoritative quarters in Berlin. On the American declaration of war, he returned to Germany and was sent as ambassador to Constantinople, where he was employed until 1918.

In various publications, and in his reminiscences on his term as ambassador in Washington, he endeavoured to prove that Germany, if it had followed the proper policy, could have avoided war with America. This statement of his views excited much controversy in his own country. When the revolution broke out in 1918, Bernstorff left the diplomatic service, but he was later active in parliamentary politics as a member of the Democratic Party in the Reichstag and also maintained a close connection with international affairs, as chairman of the German League of Nations Union until 1933. After Hitler's advent he went into exile in Geneva.