Gaetano De Sanctis (15 October 1870 – 9 April 1957) was an Italian ancient historian, classicist and lifetime senator (1950-1957). As the collection of his 'scritti minori' illustrates, his scope of scholarship ranged from Homer down to the Byzantine Empire. He was the influential teacher of Arnaldo Momigliano. His work 'Storia dei Romani' could be considered a monumental work.
De Sanctis became chair of ancient history desk at the University of Rome in 1929. In 1931, he was one of only twelve professors who refused to swear a decreed oath of allegiance to the Fascist regime () under Benito Mussolini. As a result, his professional career was severely curtailed until after World War II.
He was president of the "Istituto dell'Enciclopedia Italiana" (Treccani) from 1947 to 1954.
His shorter works are collected and indexed as:
Momigliano, A.D., 'In Memory of Gaetano De Sanctis (1870-1957)' in: idem, Studies in Modern Scholarship, ed. G.W. Bowersock and T.J. Cornell, pp. 54–71. (obituary originally published in Italian in: Rivista Storica Italiana, 69 (1957), pp. 177–195; reprinted in Momigliano's Secondo contributo (1960), pp. 299–317.)