The Actian dekanaia (Ancient Greek: δεκαναΐα, literally 'set of ten'[1]) was a Roman trophion at the Cape of Actium composed of a dedication of ten warships, which served as a memorial for Caesar Augustus' naval victory over the allies of Mark Antony and Cleopatra VII in the Battle of Actium.

[2] According to Strabo's account in Geographica, the trophy was located on the shore down the hill where the Temple of Actian Apollo stood.

It consisted of ten warships of various sizes captured from the fleets of Mark Antony and Cleopatra VII and were protected by ship sheds.

[3] The Actian dekanaia was a pivotal component of Augustus' on-site commemorative projects that were scattered around the former battlefield of the War of Actium.

The trophy was symbolically located near the navel battlefield of the Battle of Actium and probably within the area of Mark Antony's camp during the war, so as to further highlight the victory of Augustus and the defeat of his enemy.