Otto Benndorf (September 13, 1838 – January 2, 1907) was a German-Austrian archaeologist who was a native of Greiz, Thuringia.
He studied theology at Erlangen, and art history and archaeology in Bonn and Göttingen. Afterwards he worked at several high schools, including Schulpforte where one of his students was Friedrich Nietzsche. From 1864 to 1868 he took part in a scientific expedition through southern Europe to the Levant, and from 1872 to 1877 he was a professor of archaeology at the University of Prague. In 1875 he was a member of the Second Austrian expedition to Samothrace.
In 1877 Benndorf was appointed to the chair of archaeology at the University of Vienna, where he succeeded Alexander Conze (1831-1914). Here he organized several expeditions to Asia Minor, including 1881-1882 missions to Lycia in order to excavate the "Heroon of Gjölbaschi-Trysa". In 1895 he began the first Austrian excavations at Ephesus, and in 1898 was founder of the Austrian Archaeological Institute, where he worked as director for the remainder of his career.
He died in Vienna.
He was the father of physicist Hans Benndorf (1870-1953).