Otto Demus (born St. Pölten, Austria, 1902; died Vienna, 19 November 1990) was an Austrian art historian and Byzantinist. He is considered a member of the Vienna School of Art History. Between 1921 and 1928, Demus studied art history at the University of Vienna under Josef Strzygowski, receiving his Ph.D. summa cum laude. In the following years Demus travelled throughout Greece, photographing the mosaics of its Byzantine churches in color, a project that resulted in his first major publication, Byzantine mosaics in Greece (1931), written together with Ernst Diez. He also worked for Austria's historical preservation service, documenting and restoring the medieval monuments of Carinthia. In 1936 he returned to Vienna, and defended his Habilitation the following year. Armed with this necessar