Most spoken fictional language in science-fiction movies

The most spoken fictional language in a science-fiction movies is Klingon, which has appeared in seven feature films as of 31 March 2025. The language was developed in 1984 for Star Trek III: The Search for Spock (USA) by American linguist Marc Okrand.

The first appearance of the language was technically in Star Trek: The Motion Picture (USA, 1979). During the making of this film, actor James Doohan (who played "Scotty") developed a plausible-sounding nonsense language to be spoken on screen as Klingon. He taught a few phrases to actor Mark Lenard ("Sarek", father of Spock), who spoke them in the film. During the development of The Search for Spock, director Leonard Nimoy and writer Harve Bennett commissioned Marc Okrand to construct a complete fictional language based on the 12 or so words spoken on screen in Star Trek: The Motion Picture.

The seven theatrically released sci-fi films that have featured spoken Klingon are six movies from the Star Trek franchise and the 2011 science-fiction comedy Paul (USA/UK), in which a character who is a science-fiction fan attempts to communicate with a real alien using the invented language.

Klingon has made an equal number of appearances in non-science-fiction comedy movies, usually poking fun at the obsessive nature of science-fiction fandom.