The Klingons (/ˈklɪŋ.ɒn/ KLING-on; Klingon: tlhIngan [ˈt͡ɬɪ.ŋɑn]) are a fictional extraterrestrial humanoid warrior species in the science fiction franchise Star Trek.Klingons are recurring antagonists in the 1960s television series Star Trek: The Original Series, and have appeared in all five spin-off series, along with eight of the feature films.