The Breen warship was a vessel used by the Breen Confederacy in the late-24th century.

In 2366, two Breen warships attacked the Cardassian transport Ravinok forcing it to crash-land on the planet Dozaria. Its survivors were forced to work in a nearby Breen dilithium mine.

In late 2375, the Breen became allies of the Dominion, where they committed a large fleet of warships to join the war effort. Worf and Ezri Dax were brought aboard a warship after being captured by the Breen on a planet in the Goralis system.

The Federation first encountered the ships in combat during the Second Battle of Chin'toka. The Cardassian and Dominion ships held back while the Breen engaged the Federation, Klingon and Romulan forces. The ships had been equipped with energy dissipators that disabled the Allied ships' engines, weapons, and shields. The weapon was instrumental in defeating the Allied fleet and forcing the Federation Alliance from the Chin'toka system, losing the only enemy territory that they held in Cardassian space.

Fortunately, the Klingon Bird-of-Prey IKS Ki'tang was not affected, leading to a defense being discovered.

Even without the energy dampening weapon, the Breen warships proved to be formidable. One such ship destroyed Legate Damar's ship in orbit of Cardassia Prime. Several warships participated in the Battle of Cardassia. During this engagement, a Breen warship was able to outmaneuver the USS Defiant, displaying exemplary maneuverability. Several Breen warships were destroyed by the Cardassian fleet when the Cardassians joined the Allies. Breen warships were also deployed in orbit of Cardassia Prime after the Dominion's retreat.

The size of the Breen cruiser is uncertain. There are hardly any windows or other features that would allow a structural analysis. The only safe statement is that the ship must be considerably longer than the Defiant (otherwise there would be hardly any useful volume) and that it is shorter than a Jem'Hadar battlecruiser.

According to the Fact Files schematics, the pod at the aft end of the Breen ship is a detachable auxiliary craft, but this could never be seen on screen.

Breen ships are said to use organic components, according to Tuvok. This does not necessarily imply that the complete hull is made of organic matter. The hull of the Breen cruiser appears to be metallic.