Actium, Battle of, a naval engagement fought in 31 B.C. near the promontory of Actium, on the west coast of Greece. Here the forces of Octavian (Augustus) met those of Mark Antony and Cleopatra. Octavian's victory marked the end of the Second Triumvirate and the beginning of the Roman Empire. Antony's forces, resentful of being expected to fight for Cleopatra, deserted in great numbers. During the battle Cleopatra withdrew her fleet and with it escaped to Egypt. Antony followed her, leaving his fleet to conclude the battle. After several hours of fighting, the remnants of Antony's fleet managed to withdraw, but a week later surrendered.