A trireme (Latin: trirēmis "with three banks of oars"; Ancient Greek: τριήρης triērēs, literally "three-rower") was an ancient sea-faring vessel and a type of galley that was used by the ancient maritime civilizations of the Mediterranean, especially the Phoenicians, ancient Greeks, and Romans.
Triremes played a vital role in the Greco-Persian Wars, as the Achaemenid Empire used triremes to transport soldiers to battles of Marathon and Thermopylae, and the ships were the basis of the Athenian maritime empire as well as its eventual downfall in the Peloponnesian War.
Triremes were larger than biremes, whereas penteconters were smallest of the three classes. During the Peloponnesian War in the 5th century BCE the triremes were further classified into light and heavy variants, as well as elite versions of these. The heavy triremes had multiple sails and heavier artillery at their disposal than their lighter counterparts.
Behind the scenes
Characters in Assassin's Creed: Odyssey say trireme with Greek pronunciation. This is slightly false, since trireme is an English word, derived from the Latin word trirēmis. The Greek word for trireme is τριήρης (triērēs).