The Fed­er­a­tion’s greatest rival over the last cen­tury, the Klin­gon Empire occu­pies a large volume of space in the Beta Quad­rant. Klin­gon soci­ety is caste-based, dom­in­ated by the war­ri­ors of the Great Houses. Beneath them are the less­er Houses, then the com­mon pop­u­la­tion, and a dozen or so sub­ject races.

The Great Houses main­tain their own armies and fleets: in times of war these make up the Deep Space Fleet, which along with the stand­ing Intern­al Secur­ity Force, form the Imper­i­al Klin­gon Exped­i­tion­ary Forces (later renamed the Klin­gon Defense Force). The dis­par­ate nature of the fleets means that the Klin­gons oper­ate a wide vari­ety of ves­sel types, although there have been moves towards stand­ard­isa­tion since the 2250s. IKEF ves­sels are gen­er­ally divided into battle­cruis­ers and “birds-of-prey” (raid­ers), although both terms encom­pass many classes and roles.

While the major­ity of Klin­gon crew­men encountered are House war­ri­ors, noted for their tem­pers and obses­sion with per­son­al glory and hon­our, their ship crews also include tech­ni­cians and non-com­batant crew from less­er castes. Non-Klin­gons are nev­er found on Klin­gon vessels.