Oswald Samuel Konstantin Freiherr[1] von Richthofen (13 October 1847 – 17 January 1906), a German diplomat and politician, served as Foreign Secretary and head of the Foreign Office from 23 October 1900 to 17 January 1906.

The son of diplomat Emil von Richthofen (1810–1895), he was born in Iaşi, where his father was Consul General.

During his term as Director, the railway from Swakopmund to Windhoek in German South-West Africa was completed.

Richthofen became Secretary on 23 October 1900, when he succeeded Bernhard von Bülow, who at the same time became Chancellor of Germany.

On 24 January 1906, he was succeeded as Secretary by Heinrich Leonhard von Tschirschky und Bögendorff.