In the Star Trek fictional universe, the Klingon Empire is an expansionist interstellar political power, with the seat of power concentrated in the Klingon High Council on Qo'nos, ruled by a Chancellor. Their ships are basic, yet well-equipped for combat. Their military is known as the Klingon Defense Force, abbreviated KDF, and the advantages of their ships lie in numbers, and the use of cloaking devices for hit-and-run attacks. The Klingon Empire has been featured in many Star Trek video games, almost always as an antagonist within the story, although a few video games have their story focused around the Klingon Empire, such as Star Trek: Klingon, Star Trek: Klingon Academy and Star Trek: The Next Generation - Klingon Honor Guard.
Star Trek Online
In Star Trek Online, the Klingon Empire is at war with the United Federation of Planets, and had conquered both the Gorn Hegemony and the Nausicaans by the year 2409.