Otto Karl Siegfried Passarge (28 November 1866[1] – 26 July 1958) was a German geographer from East Prussia.

In 1894 Passarge took part in an expedition to Adamawa, at the northern boundary of the former German colony of Cameroon.

[2] From 1896 to 1899 Passarge worked as a geologist and surveyor for the British West Charterland Company in South Africa, during which time he made extensive ethnographic studies of the Khoisan and Bantu.

[5] Passarge's theories of racial geography (expounded in the 1920s in Das Judentum als landschaftskundlich-ethnologisches Problem) were embraced by the Nazi Party after 1933.

[6] On 11 November 1933, he was among the signatories of the commitment of the professors at German universities and colleges to Adolf Hitler and the Nazi state.