The Klingon Warbird was a type of warship designed and built by the Klingon Empire during the mid 22nd century. Vulcan diplomats warned Earth that a fleet of them might attack if provoked. (ENT episode & novelization: Broken Bow)
They were also mentioned in a museum exhibit at the Smithsonian Annex on Nova Atar III, where a control console salvaged after a battle at Crimmins VIII was on display. (TOS video game: Judgment Rites)
The designation was also applied to vessels in the mid 23rd century of the Kelvin timeline, with several appearing during the Kobayashi Maru simulation. (TOS movie, novelization & comic adaptation: Star Trek)
- It is unclear whether the usage of the term applied to a specific class, or was a general category similar to the human term "battlecruiser". The Romulans were more frequently known to use the term, but given the close proximity of the Romulan and Klingon Empires, it is unclear who originated it.