Ernst Heinrich Freiherr von Weizsäcker (25 May 1882 – 4 August 1951) was a German naval officer, diplomat and politician.

In 1916 he became a Freiherr (Baron), as his father and his family were raised to the inheritable nobility, less than two years before the fall of the Württembergish monarchy.

In 1916, he served as Flag Lieutenant to Admiral Reinhard Scheer aboard the German flagship SMS Friedrich der Grosse during the Battle of Jutland.

In 1917, during the latter portion of the First World War, he earned the Iron Cross (both classes) and was the next year was promoted to Korvettenkapitän (corvette captain) (equivalent to the British and American rank of lieutenant commander).

In 1936, as ambassador to Bern, Weizsäcker played a key role in stripping Thomas Mann of his German citizenship.

On 19 August 1938, Weizsäcker wrote in a memo to Foreign Minister Joachim von Ribbentrop: "I again opposed the whole theory of (an attack on Czechoslovakia) and observed that we should have to wait political developments until the English lose interest in the Czech matter and would tolerate our action, before we could tackle the affair without risk".

[8] He also advised the Foreign Office that drafting Jews for labour camps inside Italy would be less likely to draw a papal protest than deporting them.

[9] According to Richard J. Evans, Weizsäcker shared the opinion of Ulrich von Hassell that the Final Solution was a "devilish campaign".

[14] After the end of the war, Weizsäcker initially remained in the Vatican City with his wife, as a guest of the Pope and a member of the diplomatic corps.

Weizsäcker, with the assistance of his son, the future German President Richard von Weizsäcker, who appeared as his assistant defence counsel (Richard was a law student during the trial), claimed that he had no knowledge of the purpose for which Auschwitz had been designed and believed that Jewish prisoners would face less danger if they were deported to the East.

In October 1950, after 3 years and 3 months of detention, he obtained an early release from prison in Landsberg after a new examination of his case by the Legislative Affairs Office of the US High Commissioner for Germany, John J.

In 2010, historian Eckart Conze assessed the belief that the German Foreign Office had no involvement with Nazi war crimes in an interview:"The legend stems from individuals associated with the Weizsäcker defense.

Former diplomats, such as the brothers Erich and Theo Kordt, played a key role in the effort, as did other members of the traditional upper class, which Weizsäcker represented.