(written from a Production point of view)
This is a list of performers who were considered for roles in the Star Trek franchise, but ultimately did not appear in the role in the final episode or film.
NOTE: Performers listed here have been verified as having been considered by Star Trek personnel for a particular role on Trek in which they ultimately did not appear. Those specifically listed on this page lost out on roles on multiple Star Trek series, whereas those who lost out to roles on a specific series will be found on that corresponding series page listed below.
- See: Performers considered for TOS roles
- See: Performers considered for film roles
- See: Performers considered for TNG roles
- See: Performers considered for DS9 roles
- See: Performers considered for VOY roles
- See: Performers considered for ENT roles
- See: Performers considered for DIS roles
- Main article: Ron Canada
Ron Canada was one of two contenders for the role of Martok, alongside his good friend J.G. Hertzler. Both had the same agent at that time and at some point the agent told Canada that he got the role, though the producers still had to see one other candidate (without knowing it was Hertzler). Somehow, Hertzler ended up with the role, which made the agent tell Canada that the bad news was he didn't get the role, but the good news was it went to his best friend. 
According to Canada, not long after losing out on the role of Martok, "I missed a shot at being an admiral on Voyager because of a screw-up in an appointment." Fortunately, he was a familiar face with the casting crew, because they had him audition in "about six times a year," before being cast as Ch'Pok. "This time I was right for the role." (Starlog #226, May 1996, p. 43) Most likely, the role was Adrmial Strickler in the episode "Non Sequitur"), the only admiral to have appeared in the timeframe given.
- Main article: Kim Cattrall
Kim Cattrall was one of the final alternatives for the part of Saavik in Star Trek II: The Wrath of Khan, but she turned out to be unavailable for the filming schedule. The role went to Kirstie Alley instead. (Star Trek Movie Memories, 1995, pp. 123-124)
Claudia Christian auditioned for the role of Kira Nerys in Star Trek: Deep Space Nine.  Five years later, she auditioned for the role of Seven of Nine in Star Trek: Voyager. (Beyond the Final Frontier, p. 308)
Christian's best known role is Commander Susan Ivanova in the science fiction series Babylon 5, which she played alongside Andreas Katsulas, Bill Mumy, and Patricia Tallman. She also appeared in guest roles on numerous television series, including Quantum Leap (starring Scott Bakula and Dean Stockwell), Murder, She Wrote (co-starring William Windom), L.A. Law (starring Corbin Bernsen), Family Law, Relic Hunter, and NYPD Blue.
- Main article: Susan Diol
Chelsea Field is an actress who was considered for the role of Kira Nerys in Star Trek: Deep Space Nine, however, she turned down the offer.  Two years later, she was considered for the role of Captain Kathryn Janeway in Star Trek: Voyager, according to the TV Guide issue dated October 8-14, 1994.
Field had supporting roles in such films as Masters of the Universe (1987, with Robert Duncan McNeill and Frank Langella, Harley Davidson and the Marlboro Man (1991, also starring Branscombe Richmond, Vanessa Williams, Stan Ivar, James Nardini, Brenan Baird, and Debby Lynn Ross), and The Last Boy Scout (1991, with Bruce McGill). Although she was not given the role of Captain Janeway on Voyager, she did marry Scott Bakula, the man who took over the captain's chair on the next Star Trek series, Star Trek: Enterprise. The two met while working on the 1994 film A Passion to Kill; they married in 1996 and have two sons.
- Main article: David Gautreaux
David Gautreaux was set to play the role of Vulcan science officer Lieutenant Xon in the second Star Trek series, but the planned show was cancelled. Finally he played Commander Branch in Star Trek: The Motion Picture. (Phase II: The Lost Enterprise on Star Trek: The Motion Picture (The Director's Edition) DVD)
- Main article: Gary Graham
Gary Graham was considered and auditioned for the role of Benjamin Sisko in Star Trek: Deep Space Nine.  Two years later, he was considered for the role of Captain Janeway in Star Trek: Voyager before the decision was made that the character was to be a woman. (Confirmed by Graham at Sci-Fi Ball 24, 3 February 2018)
Kotto is known for his numerous film roles, including Mr. Big in Live and Let Die (1973), Parker in Alien (1979), William Laughlin in The Running Man (1987, with Mick Fleetwood), and FBI Agent Alonzo Mosely in Midnight Run (1988). He is also known for his role as Lt. Al Giardello on the NBC drama series Homicide: Life on the Street.
In addition, Kotto co-starred with TOS actress Nichelle Nichols in the film Truck Turner. Kotto's other film credits include 1968's The Thomas Crown Affair, 1970's The Liberation of L.B. Jones (with Anthony Zerbe), 1978's Blue Collar (with Ed Begley, Jr.), 1979's Alien, 1983's The Star Chamber (with Larry A. Hankin and James B. Sikking), and 1994's The Puppet Masters (with Julie Warner, Sam Anderson, J. Patrick McCormack, Andrew Robinson, and Michael Shamus Wiles). He has also guest-starred on such TV shows as Bonanza, Gunsmoke, Hawaii Five-O (with Jeff Corey), Fantasy Island (starring Ricardo Montalban), and The A-Team (starring Dwight Schultz). In 1977, he received an Emmy Award nomination for his performance in the TV special Raid on Entebbe, which co-starred Tige Andrews, Robin Gammell, Stephen Macht, and David Opatoshu.
Eriq La Salle
Eriq La Salle was among the actors considered for the role of Geordi La Forge. According to a 3 April 1987 memo regarding the review of an attached audition tape, sent from Bonnie Finnegan to Junie Lowry, she stated that La Salle had "an interesting look but I like Wesley Snipes better." The part ultimately went to LeVar Burton.
Several years later, La Salle was among the final group of actors considered for the role of Benjamin Sisko before the role ultimately went to Avery Brooks. (Star Trek: Deep Space Nine Companion (p. ?)) He was also briefly considered for the role of Julian Bashir. 
La Salle is best known for his role as Dr. Peter Benton on the highly acclaimed medical drama ER, which he played from 1994 to 2002. Outside ER he appeared in guest roles in series such as Spenser: For Hire (starring Avery Brooks), Quantum Leap (starring Scott Bakula and Dean Stockwell), The System, Without a Trace and 24. He also made appearances in feature films, including Coming to America (1988, with Madge Sinclair), Jacob's Ladder (1990), Color of the Night (1994, with Scott Bakula, Brad Dourif, and Jeff Corey), and One Hour Photo (2002).
La Salle is also a prolific television show director, and directed a 2015 episode of The Night Shift guest-starring Tim Russ as a high-level hospital administrator.
- Main article: Stephen Macht
Stephen Macht was considered for the role of Will Decker in Star Trek: The Motion Picture in 1978. Nine years later, he auditioned for both the roles of Jean-Luc Picard and William T. Riker in Star Trek: The Next Generation. (The Fifty-Year Mission: The Next 25 Years) Five years later, he auditioned for the role of Benjamin Sisko in Star Trek: Deep Space Nine. 
Roddy McDowall was casting director Joseph D'Agosta's choice for the role of Trelane in "The Squire of Gothos". He was overruled by producer Gene L. Coon's choice, William Campbell who seemed to be more suitable for the part. 
McDowall was an acclaimed character actor, who began his career in Hollywood as a child, acting in countless films from 1938 onward. His big break came at the age of 15 with the starring role in Lassie Come Home (1943). He also appeared in Orson Welles' 1948 film version of Macbeth, which also featured Morgan Farley. Afterwards, he appeared in numerous film and television roles, including The Longest Day (1962, with Jeffrey Hunter and John Crawford), Cleopatra (1963, with John Hoyt), Pretty Maids All in the Row (1971, with James Doohan, William Campbell, Dawn Roddenberry and written by Gene Roddenberry), The Poseidon Adventure (1972, with John Crawford, Bill Catching, and George Sawaya), and Funny Lady (1975). McDowall also voiced the role of V.I.N.CENT, a robot in Disney's The Black Hole (1979). McDowall is probably best known for his roles in four out of the five Planet of the Apes movies (which also featured James Daly, Lou Wagner, Paul Lambert, Billy Curtis, Jane Ross, Ricardo Montalban, William Windom, Jason Evers, Walker Edmiston, Janos Prohaska, James B. Sikking, Paul Comi, France Nuyen, Paul Williams, and David Gerrold), and the subsequent television series (which co-starred Mark Lenard).
On television, McDowall appeared in a famous 1960 episode of The Twilight Zone entitled "People Are Alike All Over", which co-starred Paul Comi, Susan Oliver, Byron Morrow, and Vic Perrin. He also appeared as "The Bookworm" in two 1966 episodes of Batman, which also featured John Crawford, and guest-starred in a 1972 episode of Columbo with James Gregory, William Windom, and George Sawaya.
- Main article: Eric Menyuk
Eric Menyuk was the second choice for the role of Data in Star Trek: The Next Generation, but was beaten out by Brent Spiner.  He was also considered and auditioned for the role of Odo in Star Trek: Deep Space Nine. 
Toshiro Mifune was a legendary Japanese actor appearing in almost 170 movies, best known for his roles in director Akira Kurosawa's Samurai epics. Mifune was planned to play the main Klingon villain in the proposed Star Trek movie, Planet of the Titans in 1976. (The Star Trek Compendium)
Director/screenwriter Philip Kaufman said, "My version was really built around Leonard Nimoy as Spock and Toshiro Mifune as his Klingon nemesis... My idea was to make it less "cult-ish", and more of an adult movie, dealing with sexuality and wonders rather than oddness; a big science fiction movie, filled with all kinds of questions, particularly about the nature of Spock's [duality]-exploring his humanity and what humanness was. To have Spock and Mifune's character tripping out in outer space. I'm sure the fans would have been upset, but I felt it could really open up a new type of science fiction." 
Edward James Olmos
Edward James Olmos is an Emmy Award-winning, Academy Award-nominated actor. Leonard Nimoy expressly wanted Olmos to play Kruge in Star Trek III: The Search for Spock, but the role ultimately went to Christopher Lloyd. (Star Trek III: The Search for Spock (Special Edition) special features)
A few years later, Olmos was offered the role of Jean-Luc Picard on Star Trek: The Next Generation. (Battlestar Galactica Panel, FedCon XIV, 24 May 2015; ) He had to turn it down as he was busy with other projects. His Hollywood Walk of Fame star is right next to Patrick Stewart's.
On film, Olmos is known for playing Gaff in the 1982 sci-fi thriller Blade Runner and for his Oscar-nominated role in 1988's Stand and Deliver. He received two Emmy nominations – winning his first – for his supporting role as Lt. Martin Castillo on Miami Vice. Now he has acquired new fame for his portrayal of Admiral Adama in Ronald D. Moore's hit re-imagining of the sci-fi series Battlestar Galactica, which originally aired on SyFy.
As it turned out, Olmos has been on record of being less than enamored with the science fiction genre, particularly for its portrayal of aliens, and having been seriously considered for the part of the Klingon Kruge was therefore somewhat ironic. Olmos only accepted his role in Battlestar Galactica when it became apparent to him that the series was to be primarily drama-driven and not to feature any "outlandish" life forms. (Battlestar Galactica: The Complete Series Blu-ray-special features, "Cast And Crew Take A Look Back"; "The Last Frakkin Special")
|Performers considered for Star Trek roles|
|The Original Series • Films • The Next Generation • Deep Space Nine • Voyager • Enterprise • Discovery|
Production staff members considered to work on Star Trek