Bernstorff, Johann Heinrich, Count von (1862–1939), a German diplomat. As ambassador to the United States during the first part of World War I he warned his government that unrestricted U-boat (submarine) warfare would bring the United States into the war.
Bernstorff entered the diplomatic service in 1889 and was ambassador to the United States (1908–17) and to Turkey (1917–18). He served in the Reichstag from 1921 to 1928 and was Germany's delegate to the League of Nations disarmament conferences, 1929–31. After Hitler came to power in 1933, Bernstorff went into exile in Switzerland.