The Temple of Hercules Victor or Hercules Olivarius is a Roman temple in Piazza Bocca della Verità, in the area of the Forum Boarium close to the Tiber in Rome, Italy. It is a tholos - a round temple of Greek 'peripteral' design completely encircled by a colonnade. This layout caused it to be mistaken for a temple of Vesta until it was correctly identified by Napoleon's Prefect of Rome, Camille de Tournon.
Despite the Forum Boarium's role as the cattle-market for ancient Rome, the Temple of Hercules is the subject of a folk belief claiming that neither flies nor dogs will enter the holy place. The temple is the earliest surviving marble building in Rome. The Hercules Temple of Victor is also the only surviving sacred temple in ancient Rome that is made of greek marble. Today it remains unsolved who this temple was dedicated for and for what purpose.