Guglielmo Cavallo (born 18 August 1938 in Carovigno) is an Italian palaeographer and Byzantinist, Emeritus Professor of the Sapienza University of Rome.

Cavallo graduated from the University of Bari in 1961, tutored by Carlo Ferdinando Russo; shortly after, he became assistant of Alessandro Pratesi, then Professor of palaeography and diplomatic. In 1969, he moved to Rome and first became Research assistant in Greek Palaeography at the Special School for Archivists and Librarians (then Professor of Latin Palaeography since 1975), also teaching 'Storia della tradizione manoscritta' (History of the Manuscript Tradition) at the 'Sapienza' University of Rome. In 1978, he became Professor in Greek Palaeography at Sapienza. He retired from his teaching duties in 2008 and was nominated Emeritus.