Günther was the youngest son of Baron (Freiherr) Hans Egon Friedrich Wilhelm von Reibnitz (1856–1918), who, on 19 February 1887 had married Baroness Ida Nadejda Antonie Julie Marie Eugenie Wilhelmine Friederike von Eickstedt (1867–1937), a member of the Eickstedt family, in Gieraltowitz, Upper Silesia.

Reibnitz was born on 8 September 1894 at Mistitz in the Prussian province of Silesia, now called Miejsce Odrzańskie, having since become part of Poland.

[6] After separating from his wife, Reibnitz established a farm at Hahnenvorwerk, near Silverberg in Silesia, breeding animals for the fur trade.

His only daughter out of this marriage Margarita Maria Elisabeth Agathe Alice Freiin von Reibnitz (1924-2012) married Charles Jacques Francisco (b.

By reaffirming his loyalty, he was able to extract himself from the affair; he had also referred to the leader of the SS, Heinrich Himmler, as the "chicken farmer".

[8] Soon after he rejoined the armed forces on active service, Reibnitz was sent back to the home front due to heart problems.

Because his wife was already under observation by the Gestapo over her contacts before the war with supposed British Secret Service agents,[4] as well as in connection with a range of essentially minor "transgressions", his situation became increasingly critical, and in 1944 he was dismissed from the Nazi Party, from the Cavalry SS, and from the post of Regional Director of Hunting for Silesia.

[4][9][10] On 16 November 1942, Reibnitz's son Friedrich was born in Breslau, and on 15 January 1945 his daughter Marie Christine (the later Princess Michael of Kent) was born in Karlsbad (now Karlovy Vary in the Czech Republic), near the estate of her maternal grandmother Princess Hedwig of Windisch-Graetz (1878–1918), a daughter of Alfred III, Prince of Windisch-Grätz, 11th Minister-President of Austria.

In the confusion towards the end of the war, Reibnitz managed to avoid being transferred, on the personal orders of Himmler, to the Dirlewanger special unit, and was able to find refuge with his old army regiment.

Margarita, Reibnitz's daughter from his first marriage, married Charles Jacques Francisco in Sharon, Connecticut, on 14 September 1947.

On 30 June 1978 in Vienna, Reibnitz had attended the civil wedding of his daughter Marie Christine to Prince Michael of Kent.

A biography of Elizabeth II by John Parker states that by the end of the Second World War, the Berlin Documents Centre had held a dossier on Reibnitz said to be four inches thick.

[17] Writer Barry Everingham stated that "historians at the Yad Vashem Institute in Jerusalem claimed that the baron was planted in the SS to act as Goering's spy".