Guy Thompson Griffith, FBA (7 January 1908 – 10 September 1985) was an English ancient historian and classicist.
Graduating with a first-class degree, Griffith was awarded a studentship and studied German in Vienna.
Initially, he studied ancient Greek soldiers; two years later, he won the Hare Prize for an essay on the topic and in 1935 he published Mercenaries of the Hellenistic World.
Appointed a university lecturer in 1937, he began focusing on fourth-century Greek history but his work at Cambridge was interrupted by service in the Royal Air Force Volunteer Reserve from 1941 to 1945.
At the end of the Second World War, he returned to teaching at the university and his college, and was appointed co-editor of The Classical Quarterly in 1947 (remaining in office until 1951).