Klingons (Klingon: tlhIngan; Pronunciation: /ˈt͡ɬɪŋɑn/) are a warrior race in the fictional Star Trek universe. They were in the show Star Trek: The Original Series (TOS) many times and were in all five spin-off series afterwards, eventually becoming friends of the United Federation of Planets.

Made by writer Gene Coon, Klingons were introduced in the episode "Errand of Mercy" (1967). They were named for Lieutenant Wilbur Clingan, who served with Star Trek creator Gene Roddenberry in the Los Angeles Police Department.