A constructed language that was explicitly made for a work of fiction.

Can be written in a real writing system such as Latin or Cyrillic (usually to represent a spoken fictional language), or in its own unique script (which is usually Latin in a unique script to represent a written fictional language).

Note that like for real languages tagged on e621, specific fictional languages' tags need to have _text or _audio as a suffix depending on the context.

Tagged specific fictional languages

• furbish_text (Furby) – The native language of the Furbies, consisting of "simple syllables, short words, and various sounds" according to the Furby Wikipedia article. Furbies speak English over time from play with the user.
• na'vi_text (James Cameron's Avatar) – The native language of the Na'vi, which is also a real constructed language made to flesh out the world of Pandora in the franchise. There is no native script for the language, so Latin characters are used.
• tantalog_text (Lilo & Stitch) – Stitch and the experiments' native language; the written form (which is basic English and Hindu–Arabic numerals in an alien script) is a lingua franca in the United Galactic Federation, while the spoken form is a semi-consistent gibberish developed by the writers of Lilo & Stitch: The Series based on Stitch's dialogue from the first film.
• yautja_text (Predator) – The native language of the yautja (the Predators).

Tagged specific fictional written languages and writing systems

• aurebesh_text (Star Wars) – Written language alphabet to represent Galactic Basic (i.e. English) in the Star Wars universe, with its letters corresponding to all English letters and certain English digraphs. Designed by art director Stephen Crane in the early 1990s based on shapes designed by Joe Johnston, standardizing the letters based on shapes similar to Eurostile.