Thucydides was a fifth century BCE Greek historian best known for his history of the Peloponnesian wars. The head is identified by its resemblance to a double herm with Herodotus, on which he is named.

This portrait is the finest of six surviving versions of the same lost bronze prototype, and was brought to Britain during the Grand Tour period, in 1754. The prototype is unlikely to date from the lifetime of Thucydides as he was sent into exile in his later years, and his popularity was revived only after his death