31 BC

Battle of Actium

Battle of Actium: Octavian and Agrippa defeat Antony and Cleopatra's fleet

Cleopatra's 60 ships hoisted sail and passed through the middle of a battle that had not yet been decided — and Antony left his flagship to follow her.

2 September 31 BC: outside the Ambracian Gulf

The date is unusually secure — Cassius Dio explicitly gives 2 September 31 BC. Off Actium in western Greece, the fleets of Octavian and of Mark Antony and Cleopatra met outside the gulf's entrance, after a campaign in which Marcus Agrippa's naval operations had cut Antony's maritime communications and contributed to shortage, disease and desertion in his camp.

Agrippa directed Octavian's naval effort, commanding the left wing while Octavian held the right. When Antony's heavy ships came out of the narrows after midday, Octavian's lighter vessels avoided direct ramming and swarmed individual heavy ships in groups — fighting Plutarch compares to storming walled towns.

The squadron that sailed through the middle

Cleopatra's squadron of 60 ships, positioned behind the line, raised sail and broke through the combat toward the Peloponnese — she did not sail in from elsewhere to rescue Antony. Whether this was panicked flight, an agreed breakout carrying the treasury, or a contingency plan remains debated; the ancient accounts are hostile witnesses.

Antony left his flagship in a smaller vessel and followed her. Plutarch adds that after boarding Cleopatra's ship he sat alone at the prow for three days, head in his hands. His fleet fought on without him before surrendering or being captured; Plutarch — citing Octavian's own account — reports no more than 5,000 dead and 300 ships taken, and a land army that waited seven days for its commander before defecting.

Decisive — but not the end

Actium did not kill Antony and Cleopatra or conquer Egypt. Both escaped; Octavian consolidated Greece and Asia, returned briefly to Italy, and took Alexandria only in 30 BC, the year both died in Egypt.

What the day did decide was mastery of the Roman world. Cassius Dio dates Octavian's sole power from Actium — though Antony and Cleopatra held Egypt until 30 BC, and Octavian's constitutional supremacy was constructed through the settlements of 27 and 23 BC.

Sources

Researched 23 Aug 2026 6 sources 3 audit passes Date corrected

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date corrected. The research places this at -0031-09-02.

What the sources leave uncertain

The date is unusually secure because Cassius Dio explicitly gives 2 September.
Ancient accounts are hostile to Antony and Cleopatra and disagree in interpretation. Cleopatra’s departure may have been a panicked flight, an agreed breakout carrying the treasury, or part of a contingency plan.
Ancient fleet and casualty figures vary and should be attributed to their authors rather than treated as exact modern counts.
Cassius Dio retrospectively dates Octavian’s sole rule from Actium, but Antony and Cleopatra remained alive and controlled Egypt until the following year.