Roberto Weiss (21 January 1906 – 10 August 1969) was an Italian-British scholar and historian, who specialised in the fields of Italian-English cultural contacts during the period of the Renaissance, and of Renaissance humanism.
Weiss originally came to Britain to study law at Oxford University. He worked for a short time from 1932–1933 in the Department of Western Manuscripts of the Bodleian Library, and obtained his D.Phil from Oxford in 1934, in the same year winning the Charles Oldham prize. He was naturalised British in 1934. The author John Buchan became his friend and mentor. He also met the novelist Barbara Pym, who later used him as the basis for the character Count Ricardo Bianco in her first novel, Some Tame Gazelle (1950), which she had begun writing while at Oxford. During World War II, between 1942 and 1945, he served in the British Royal Artillery in a non-combatant role.
Other than his period of military service, Weiss taught at University College, London from 1938 until his death. He became Professor of Italian in 1946.
He was a pioneer in the study of early humanism. His first book (based on his thesis), Humanism in England during the Fifteenth Century (1941, subsequent editions: 1955, 1967, 2009) was the first full-length monograph in English to treat the subject of the pre-Tudor influence of Italian humanism on England. A reviewer from its first publication said that "young Weiss's meticulous scholarship had already long been recognised", and it was elsewhere described as "the best general guide" to its subject, and as the work in whose shadow other scholars remained seven decades later. The book was also criticised for adhering too much to Jacob Burckhardt. Subsequent lines of research took in Italian pre-humanists and the Renaissance knowledge of Greek. Weiss cited Rosamond Joscelyne Mitchell in this book, and she cited him in her book From Bristol to Rome in the Fifteenth Century.