(written from a Production point of view)
Numerous undeveloped Star Trek episodes were written for various Star Trek series that were submitted or developed for production, but for various reasons never aired, as was the case with several other undeveloped Star Trek projects.
Star Trek is..., the very first series outline, listed a number of short ideas for episodes, some of which were later worked out. David Gerrold presents his case of failed story, outline or script submittals during his early attempts to write for Star Trek: The Original Series. These outlines were later presented in his book The Trouble with Tribbles.
James Van Hise further explored in his 1992 book, Trek: The Unauthorized Behind-The-Scenes Story of The Next Generation, several other unfilmed or unproduced episodes written for Star Trek: The Next Generation, most notably the controversial episode, written by Gerrold, entitled "Blood and Fire".
In his introduction to the 1994 book Lost Voyages of Trek and The Next Generation (p. 3), Edward Gross commented, "Perhaps most surprising in the Star Trek mythos is the sheer quantity – and in many cases quality – of unfilmed adventures that have spanned from the original through various aborted attempts at revival throughout the 1970s and right in to The Next Generation. In many cases, these scripts and treatments were left unfilmed due to political reasons, studio indecisiveness or ego. In others, they just weren't up to snuff and probably wouldn't have made a decent episode of Lost in Space.
- Undeveloped Star Trek: The Original Series episodes
- Undeveloped Star Trek: The Animated Series episodes
- Undeveloped Star Trek: The Next Generation episodes
- Undeveloped Star Trek: Deep Space Nine episodes
- Undeveloped Star Trek: Voyager episodes
- Undeveloped Star Trek: Enterprise episodes
- Undeveloped Star Trek: Discovery episodes