Otto Pius Hippius (born May 17, 1826, Saint Petersburg, Russia — died September 10, 1883, Saint Petersburg, Russia) was a Baltic German architect, particularly noted for several buildings in present-day Estonia. Otto Hippius was born in the family of a painter and lithographer Gustav Adolf Hippius who taught his son Art since the earliest childhood. At the teenage age Otto Hippius studied in Germany and in 1849 he graduated with honors from Karlsruhe Institute of Technology. Since 1849 to 1851 he studied at the Russian Academy of Arts in Saint Petersburg and upon graduation continued working as an architect and teacher at several art schools. In 1864 Hippius became a member of the Russian Academy of Sciences and in 1879 he became a professor.