A fire ship or fireship, used in the days of wooden rowed or sailing ships, was a ship filled with combustibles, deliberately set on fire and steered (or, where possible, allowed to drift) into an enemy fleet, in order to destroy ships, or to create panic and make the enemy break formation. Ships used as fire ships were either warships whose munitions were fully spent in battle, or surplus ones which were old and worn out, or purpose-built inexpensive combustible vessels rigged to set afire, stir toward targets and maintain course, and abandoned quickly by the crew.
An explosion ship or hellburner was a variation on the fire ship, intended to cause damage by blowing up in proximity to enemy ships.
Fireships were famously and cleverly used to great effect by the outgunned English fleet against the Spanish Armada during the Battle of Gravelines.
Possibly the oldest account of the military use of a fire ship is recorded by the Greek historian Thucydides on the occasion of the failed Athenian Sicilian Expedition (415–413 BC). In the episode, the Athenian expeditionary force successfully repels an attack by the Syracusans:
The rest [of the Athenian force] the enemy tried to burn by means of an old merchantman which they filled with faggots and pine-wood, set on fire and let drift down the wind which blew full on the Athenians. The Athenians, however, alarmed for their ships, contrived means for stopping it and putting it out, and checking the flames and the nearer approach of the merchantman, thus escaped the danger.
A fire ship was used in the Battle of Red Cliffs (208) on the Yangtze River when Huang Gai assaulted the enemy naval force with a fire ship filled with bundles of kindling, dry reeds, and fatty oil.
Fire ships were decisively employed by the Vandals against the armada sent by the Eastern Roman Empire, in the Battle of Cap Bon (468).