(written from a Production point of view)
Many projects have been partially developed for Star Trek beginning in the 1970s. There have also been deleted scenes for completed projects.
- Star Trek: Planet of the Titans (1976-1977)
- Star Trek: The First Adventure (1989)
- Star Trek: IMAX (1997)
- Star Trek: The Beginning (2005)
Untitled movie project
Gene Roddenberry approached Paramount Pictures with the idea of a Star Trek movie as early as 1973. Roddenberry wanted Herb Solow (formerly the Desilu executive in charge of production on the first two seasons of Star Trek) to produce the film. He also wanted Solow to negiotiate with Paramount in his behalf. Roddenberry based the plot idea on the outline "A Question of Cannibalism" in his 1964 series proposal, Star Trek is... (the title was reworked as "The Cattlemen"). Solow thought the script had to be heavily rewritten, because "it did not foreshadow an enjoyable night at the movies". Despite this, Paramount was eager on the project, however Roddenberry refused to accept the screenwriting fee and equity proposed by the studio. After several unsuccessful negiotiations, Paramount backed away from the project and the movie was never made. Solow commented that the studio could've made the film without Roddenberry, but they did not want to alienate the fanbase. (Inside Star Trek: The Real Story, pp. 420-421, 430)
An eleventh Star Trek movie was initially planned during production on the tenth film, Star Trek Nemesis. Nemesis co-writers John Logan and Brent Spiner intended to follow that film with a "crossover" sequel. After Nemesis failed financially, however, this plan was abandoned. 
Live-action television series
- Assignment: Earth (1967-1968) 
- There were some plans for a fourth season of Star Trek: The Original Series, including a second episode featuring Kor, that would have aired 1969-1970.
- Shortly after the cancellation of TOS, Paramount proposed a spin-off series centered on the character of Spock, featuring him living on Vulcan with other Vulcans. This idea was turned down by Gene Roddenberry, who Paramount had asked to produce the series. (The Making of Star Trek: The Motion Picture, p. 18)
- Star Trek: Phase II (1977)
- Before the creation of Star Trek: The Next Generation, Paramount showed Roddenberry a script for a possible new Star Trek television series involving the Enterprise being run by a group of cadets. Roddenberry was against this. ("Gene Roddenberry - The Creator of Star Trek: The Next Generation", The Official Star Trek: The Next Generation Magazine Vol. 1, p. 4)
- There were some plans for a fifth season of Star Trek: Enterprise, which would have aired 2005-2006.
- Undeveloped Star Trek episodes
- Babylon 5 creator J. Michael Straczynski and Bryce Zabel (Dark Skies) proposed a reboot of the franchise with the crew of the original series in 2004, but Paramount ignored the proposal as they were not "even willing to talk about Star Trek".
- Jonathan Frakes developed a Star Trek series that was rejected by Paramount, who stated that they had previously rejected proposals by William Shatner and Bryan Singer out of concern of "franchise fatigue". Frakes agreed that this was a wise decision, "Not that [I] wouldn't love the Titan, or the Rikers in Space, or any of those shows on the air." 
- Bryan Singer, Christopher McQuarrie, Robert Meyer Burnett and Geoffrey Thorne planned to pitch their own show entitled Star Trek: Federation, but they chose not to after development of Star Trek was announced. 
Animated Star Trek
- Star Trek: Final Frontier (2006)
Before the making of Star Trek: The Animated Series was given the go-ahead, one concept for an animated series that was offered to Gene Roddenberry involved the Enterprise crew landing on strange planets and shooting everything on sight that was different or seemed ugly. (The Making of Star Trek: The Motion Picture, p. 18)
1990 animated Star Trek
In 1990, Paramount Pictures attempted to sell an idea for an animated series that combined characters from Star Trek: The Next Generation and Star Trek: The Original Series. None of the networks or syndicators at the time were interested in the series and it was unsold. Rick Berman said such a project would have "diluted the franchise."
Cel art from this series has been seen in various Star Trek conventions over the years, and it has been stated to be well-drawn.
CGI cartoon based on the original series
In the late 1990s, Paramount briefly considered creating CGI original series cartoon inspired by the success of Roughnecks: Starship Troopers Chronicles, and the art (using motion capture for the characters) of the unreleased game Star Trek: Secret of Vulcan Fury. 
Star Trek: The Lions of the Night
Around 2003 Star Trek: The Lions of the Night was the concept by writer Jimmy Diggs to produce a movie era CGI animated Star Trek adventure. He described the plot the following way: "... Captain Sulu takes command of the USS Enterprise-B and must stop a Kzinti invasion of Federation Space." Artist Court Jones created several sketches to depict a new concept of Kzinti that were looking more dangerous as well as a concept of how the Kzinti assault fleet would look.
The material of this animated series was recycled by the writer for an article in Star Trek: Communicator (issue #149) and later for the undeveloped Star Trek: Enterprise season 5 episode "Kilkenny Cats".