A trireme (derived from Latin: "tres remi:" "three-oar;" Greek Τριήρης, literally "three-oarer") was an ancient vessel and a type of galley, a Hellenistic-era warship that was used by the ancient maritime civilizations of the Mediterranean, especially the Phoenicians, ancient Greeks and Romans.
The trireme derives its name from its three rows of oars on each side, manned with one man per oar. The early trireme was a development of the penteconter, an ancient warship with a single row of 25 oars on each side, and of the bireme (Greek: διήρης), a warship with two banks of oars, probably of Phoenician origin. As a ship it was fast and agile, and became the dominant warship in the Mediterranean from the 7th to the 4th centuries BC, when they were largely superseded by the larger quadriremes and quinqueremes. Triremes played a vital role in the Persian Wars, the creation of the Athenian maritime empire, and its downfall in the Peloponnesian War.
In English, no differentiation is made between the Greek triērēs and the Latin triremis. This is sometimes a source of confusion, as in other languages these terms refer to different styles of ships. Though the term today is used almost exclusively for ancient warships, modern historians also refer to medieval and early modern galleys with three banks of oars per side as triremes. The rowing arrangement of these differed considerably, though, since knowledge of the multi-level structure of the original triremes was lost some time during Late Antiquity.