The Eulenburg expedition was a diplomatic mission conducted by Friedrich Albrecht zu Eulenburg on behalf of Prussia and the German Customs Union in 1859-62. Its aim was to establish diplomatic and commercial relations with China, Japan and Siam.
In 1859, King Prince William, who was acting as Regent for his seriously ill brother Friedrich Wilhelm IV, appointed Friedrich Albrecht Count of Eulenburg Extraordinary Envoy to a Prussian Mission to Eastern Asia.
The major participants of the expedition were Friedrich Albrecht zu Eulenburg, Lucius von Ballhausen (doctor), Max von Brandt (attaché), Wilhelm Heine (painter), Albert Berg (artist), Karl Eduard Heusner, Fritz von Hollmann, Werner Von Reinhold, Ferdinand von Richthofen and Gustav Spiess.
The expedition was provided with three warships from the Prussian East Asian Squadron, the SMS Arcona, the SMS Thetis and the SMS Frauenlob.
Before the expedition even reached Japan, the Frauenlob was lost in a typhoon outside Yokohama on 5 September 1860, losing its entire crew of five officers and 42 men, and the two remaining ships decided to anchor in Edo Bay. The negotiations with the Bakufu were protracted and would last for several months.