Actium (ăk´tēəm, –shē–), promontory, NW Acarnania, Greece, at the mouth of the Ambracian Gulf. There are vestiges of several temples and an ancient town. At Actium was fought the naval battle (31 BC) in which the forces of Octavian (later Augustus) under Agrippa defeated the sea and land forces of Antony and Cleopatra. The battle established Octavian as ruler of Rome. The Actian games, held at Nicopolis every four years, were established to commemorate the event.