Klingons (Klingon: tlhIngan, pronounced ) are a fictional warrior race in the Star Trek universe.
Klingons are recurring villains in the 1960s television show Star Trek: The Original Series, and have appeared in all five spin-off series, along with eight of the feature films. Initially intended to be antagonists for the crew of the USS Enterprise, the Klingons ended up a close ally of humanity and the United Federation of Planets in Star Trek: The Next Generation and Star Trek: Voyager. In the 1990s series Star Trek: Deep Space Nine the United Federation of Planets briefly goes to war with the Klingons. Later in the series, the two join together with the Romulans to fight the Dominion.
As originally developed by screenwriter Gene L. Coon, Klingons were darkly colored humanoids with little honor, intended as an allegory to the Cold War tensions between the United States and the Soviet Union, though Star Trek creator Gene Roddenberry did not aspire to any political parallels. With a greatly expanded budget for makeup and effects, the Klingons were completely redesigned in Star Trek: The Motion Picture (1979), gaining ridged foreheads that created a continuity error not explained by Star Trek canon until 2005. In later films and the spin-off series Star Trek: The Next Generation, the militaristic traits of the Klingons were bolstered by an increased sense of honor and strict warrior code.
Among the elements created for the revised Klingons was a complete language, developed by Marc Okrand off gibberish suggested by actor James Doohan. Klingon has entered popular culture; the works of William Shakespeare and even parts of the Bible have been translated into the glottural language. A dictionary, a book of sayings, and a cultural guide to the language have been published. In addition, according to Guinness World Records, Klingon is the most popular fictional language by number of speakers.