Oswald Freiherr von Richthofen, GCVO (13 October 1847 – 17 January 1906) was a German diplomat and politician, who 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. He joined the foreign service in 1875, and served in the Franco-Prussian War 1870–1871. From 1885 to 1896, he was stationed in Cairo. He served as Director of Colonial Affairs at the Foreign Office from 15 October 1896 to 31 March 1898. During his term as Director, the railway from Swakopmund to Windhoek in German South West Africa was completed. A post office in the colony is named in his honour.
He was appointed Under-Secretary of Foreign Affairs in December 1897.
Richthofen became Secretary on 23 October 1900, when he succeeded Bernhard von Bülow, who at the same time became Chancellor of Germany. He served as Secretary until his death in Berlin on 17 January 1906. He was also appointed Privy Councillor in 1901 and Minister of State of Prussia in 1905. On 24 January 1906, he was succeeded as Secretary by Heinrich Leonhard von Tschirschky und Bögendorff.