| Character | Actor | Appearances | Description |
| Stephen Davies | Darkling | Mikhal Traveler and owner of a lodge. |
| Clyde Kusatsu | The Measure of a Man, Phantasms, All Good Things... | A Starfleet Admiral. |
| Darryl Henriques | TUC | Romulan ambassador to the Federation in 2293. Involved in the assassination of Klingon Chancellor Gorkon. |
| | Masks | A teacher who supervised Eric Burton's art class. |
| Natalija Nogulich | Chain of Command, Part I ; The Maquis, Part II | Starfleet Admiral involved in negotiations over the Cardassian Demilitarized Zone. A simulated version of the Admiral was used by the Dominion to test the reaction of Sisko and Starfleet in general to a Dominion attempt to gain a foothold in the Alpha Quadrant. |
| Robin Christopher | Duet, In the Hands of the Prophets | Bajoran engineer aboard Deep Space Nine; secretly working for Winn Adami. |
| Neelix | Ethan Phillips | Caretaker | Talaxian ship's cook, morale officer, and chief ambassador of the. |
| Rachen Assapiomonwait | The Schizoid Man | Engineer on the USS Enterprise-D during the 2360s; recurring uncredited background character. |
| Eric Bana | ST09 | Romulan captain of the 24th-century mining vessel Narada; transported through time on his quest for vengeance for the destruction of his home planet. |
| Valerie Wildman | Message in a Bottle | Romulan officer involved in hijacking the USS Prometheus NX-59650, an experimental prototype Federation starship. |
| Isaac Newton | John Neville Peter Dennis | Descent, Part 1, Death Wish | Famous Earth physicist, recreated in the holodeck for a game of poker with Data. Also summoned by "Q" to the USS Voyager to testify at Quinn's asylum hearing. |
| Salli Richardson-Whitfield | Second Sight | Halanan wife of terraformer Gideon Seyetik. By "psychoprojective telepathy", she creates an alter ego, Fenna, who fell in love with Benjamin Sisko. |
| Henry Gibson | Profit and Lace | Slug-O-Cola tycoon and commissioner of the Ferengi Commerce Authority. |
| Avery Brooks | Our Man Bashir | A mad scientist in Bashir's secret agent program. Temporarily altered by a transporter malfunction to look like Benjamin Sisko. |
| Marianna Hill | Dagger of the Mind | A medical officer on the Enterprise, specializing in psychiatry and penology. |
| Nog | Aron Eisenberg | Emissary | Son of Rom and nephew of Quark; first Ferengi in Starfleet |
| Robert DoQui | Sons of Mogh | Old family friend of Worf who takes Kurn into his family. |
| None | TMP, books | Starfleet Commanding Admiral and old friend of the Kirk family. |
| Vic Perrin | The Changeling | Hybrid of an Earth space probe and an alien probe. Driven to sterilize imperfection. |
| Richard Tatro | I, Mudd | An android who infiltrates and hijacks the Enterprise. |
| Lori Petty | Gravity | Survives on a Class D planet for several years. Falls in love with Tuvok. |
| Scott MacDonald | Face of the Enemy | Romulan subcommander of the IRW Khazara and a member of Ambassador Spock's underground movement on Romulus. |
| Character | Actor | Appearances | Description |
| Saavik | Kirstie Alley, Robin Curtis | WOK, SFS, TVH | Vulcan-Romulan Starfleet lieutenant junior grade; Spock's protege. |
| Rocco Sisto | Sarek | Assistant to Sarek during the Legaran negotiations. |
| Jaime Hubbard | The Dauphin | Future ruler of Daled IV, ferried to her planet by the Enterprise-D. |
| Sarek | Mark Lenard, Jonathan Simpson, Ben Cross, James Frain | Journey to Babel, Sarek, Redemption, TMP, SFS, TVH, TFF, TUC, ST09 | Vulcan ambassador; father of Spock and Sybok. |
| Nikki Cox | Pen Pals | Native of a seismically active planet and friend of Data. |
| Saru | Doug Jones | DSC, "The Brightest Star" | Kelpien First Officer of the USS Discovery. |
| Tarik Ergin | Night | Robot character in The Adventures of Captain Proton holodeck program. |
| Jean Simmons | The Drumhead | Starfleet admiral and head of a paranoia-fueled investigation aboard the Enterprise-D. |
| Eric Pierpoint | For the Uniform | Captain of the starship Malinche assigned to take up the search for renegade Michael Eddington after the Defiant becomes disabled. |
| Montgomery Scott | James Doohan, Simon Pegg, Martin Quinn | Hegemony , TOS, TAS, TMP, WOK, SFS, TVH, TFF, TUC, GEN, Relics, ST09, STID, STB | Chief Engineer of the USS Enterprise and Enterprise-A under Captain Kirk. |
| Ursaline Bryant | Conspiracy | Starfleet captain; helps warn Picard of an alien takeover of Starfleet. |
| Ronald Robinson | Repression | Firstborn son of Tuvok and T'Pel. |
| Denise Crosby | The Mind's Eye, Redemption, Part II, Unification, Part II | Romulan commander and hybrid daughter of an alternate timeline version of Tasha Yar. Supervises the "conditioning" of Geordi La Forge aboard her Warbird, provides weapons to the House of Duras in the Klingon Civil War, and coordinates a plan to invade the planet Vulcan. |
| Suzie Plakson | The Schizoid Man | Vulcan Starfleet medical officer and lieutenant on the Enterprise-D. |
| Sierra Pecheur | Data's Day | Romulan subcommander. In her undercover identity as Vulcan ambassador T'Pel, one of the Federation's most honored diplomats. |
| Ian Wolfe | Bread and Circuses | Roman citizen and Sun worshipper on planet 892-IV. |
| Seska | Martha Hackett | Parallax | Cardassian undercover operative; infiltrates the Maquis posing as a Bajoran and is stranded with the rest of the crew in the Delta Quadrant. Later, joins the Kazon-Nistrim and becomes an enemy of the Voyager crew and Captain Kathryn Janeway. |
| Seven of Nine | Jeri Ryan | Scorpion Part II ; Absolute Candor | Former Borg drone, liberated by the and thereafter a member of its crew. Later, member of the Fenris Rangers, then Commander and subsequently Captain of the USS Titan/ "Enterprise- G" |
| Richard Kiley | Second Sight | Terraformer. |
| Shakaar Edon | Duncan Regehr | Shakaar ; | Leader of Bajoran resistance during Cardassian occupation; later, First Minister of Bajor. |
| Elizabeth Dennehy | The Best of Both Worlds, Võx, Star Trek: New Frontier spin-off novels. | Starfleet Lieutenant Commander assigned to the Enterprise-D to provide assistance against the Borg. Field-promoted to commander and first officer when Picard was assimilated. Becomes fleet admiral before the events of Star Trek: Picard and briefly commands the Enterprise-F before the Borg kill her in 2401. |
| Benjamin W.S. Lum | The Naked Now | Assistant chief engineer on the Enterprise-D in 2364. Under the influence of the polywater intoxication, removes all the isolinear chips from the engine control station. |
| Tom Hardy | NEM | An imperfect clone of Captain Jean-Luc Picard created by the Romulans with the intent of replacing Picard. This plan is abandoned and Shinzon is exiled to Remus, where he leads soldiers during the Dominion War. Later, seizes control of the Romulan Senate in a coup d'etat, and lures Picard to the planet with peace overtures. |
| Jeffrey Combs | The Andorian Incident | Andorian commander of the Andorian Imperial Guard starship Kumari. Assists Jonathan Archer in impeding the Xindi superweapon's deployment against Earth. |
| Reggie Nalder | Journey to Babel | Andorian ambassador to the 2267 "Babel" conference regarding the admission of Coridan into the Federation. |
| James Cromwell | Birthright | Yridian with information to sell about Klingons captured by Romulans at Khitomer. |
| None | Novelisations | Insectoid representative on the Xindi Council. |
| Khan Noonien Singh | Ricardo Montalbán, Benedict Cumberbatch | Space Seed, WOK, ID | Genetically enhanced superman from the mid-1990s. Attempts to seize control of the Enterprise and is marooned on Ceti Alpha V by James Kirk; 15 years later, takes revenge by hijacking the USS Reliant NCC-1864 and attacking the Enterprise. |
| Michael Mack | The Pegasus | Romulan commander of the IRW Terix, assigned to locate and retrieve the USS Pegasus NCC-53847. |
| Benjamin Lafayette Sisko | Avery Brooks | Emissary | Commanding officer of Starbase Deep Space 9 and Emissary to the Bajoran Prophets. Promoted from commander to captain after nearly three years at DS9. Father of Jake Sisko and widower of Jennifer Sisko. |
| Jake Sisko | Cirroc Lofton, Thomas Hobson, Tony Todd | Emissary | Son of Benjamin and Jennifer Sisko. |
| Felecia M. Bell | Emissary | Wife of Benjamin Sisko and mother of Jake Sisko. Killed at Wolf 359, but survived in the mirror universe. |
| Joseph Sisko | Brock Peters | Homefront | New Orleans restaurateur and father of Benjamin Sisko. |
| Galyn Görg | The Visitor | Bajoran wife of Jake Sisko in an alternate future. |
| Shannon Fill | The First Duty, Lower Decks, various novelisations | Bajoran Starfleet officer. While a cadet, implicated in the death of a fellow cadet. As a security ensign aboard the Enterprise-D, killed on a mission to return Cardassian double agent Joret Dal to his home territory. |
| Jacqueline Schultz | Extreme Measures | Wife of Section 31 operative Luther Sloan. |
| Luther Sloan | William Sadler | Inquisition | Section 31 operative who repeatedly attempts to recruit Bashir. |
| Alfre Woodard | FCT, Fissure Quest | Twenty-first-century human treated for radiation poisoning on the Enterprise. Assists Zefram Cochrane in building the Phoenix, the first warp-capable ship on Earth. Alternate universe Sloane in LOW, where she assisted Cochrane in building the first quantum reality drive, then commands the Beagle in exploring the multi-verse. |
| Andrea Dromm | Where No Man Has Gone Before | Command-division yeoman on the Enterprise; close to Gary Mitchell. |
| Isa Briones | Remembrance | Data's daughter. |
| James Otis | 'Til Death Do Us Part, Strange Bedfellows, The Changing Face of Evil | Bajoran Ranjen who serves as loyal assistant to Kai Winn until she stabs him in the back, killing him. |
| Jon Rashad Kamal | TMP | Vulcan Starfleet commander assigned to the Enterprise as science officer during the V'Ger crisis. Killed in a transporter accident while beaming up. |
| Adam Soong | Brent Spiner | Fly Me to the Moon | Unethical geneticist whose methods cause his research license to be revoked. While looking for a cure for his daughter Kore's genetic disease, he is approached by Q and later by the Borg Queen, who lure him into helping them and opposing Picard. Ancestor of Noonien Soong. |
| Altan Inigo Soong | Brent Spiner | Et in Arcadia Ego, The Bounty | Son of Noonien Soong, and Data's human "brother". Co-creator of the Asha twins along with Bruce Maddox, and later the developer of the "golem" android. Briefly appears as a hologram in the Daystrom Institute. |
| Arik Soong | Brent Spiner | Borderland | Criminal creator of genetically engineered humans. Ancestor of Noonien Soong. |
| Fionnula Flanagan | Inheritance | Deceased wife of Noonien Soong, whose consciousness was transferred at her death to an identical Soong-type android. |
| Brent Spiner | Brothers | Human cyberneticist; father of Altan, husband of Juliana, and creator of Data, Lore, a replica of Juliana, B-4, and two other prototype androids. Like Khan Noonien Singh, named for a friend of Gene Roddenberry's. |
| Malcolm McDowell | GEN | El-Aurian scientist desperate to return to the Nexus. |
| Max Grodénchik | Captain's Holiday | Ferengi seeking to profit from an archaeological search for the Tox Uthat. |
| Soval | Gary Graham | Broken Bow | Vulcan ambassador to Earth in the 22nd century. |
| Spock | Leonard Nimoy, Ethan Peck, Zachary Quinto | TOS, TAS, Unification I & II, DSC, SNW, TMP, WOK, SFS, TVH, TFF, TUC, ST09, STID, STB | Son of Vulcan ambassador Sarek and human Amanda Grayson. Science Officer and First Officer on the and, subsequently, the USS Enterprise-A; Captain at Starfleet Academy; Federation Ambassador. |
| Spot | | Data's Day , GEN, NEM | Data's pet cat. |
| John Durbin | Lonely Among Us | Selay delegate to the summit with the Anticans on Parliament. |
| Ed Begley, Jr. | Future's End | 20th-century pothead-turned-entrepreneur after discovering a 29th-century spacecraft that crash-lands near his campsite. |
| Larc Spies | The Forge | Vulcan chief investigator of the Vulcan Security Directorate in 2154. Carries a bomb into the United Earth Embassy on Vulcan. |
| Charles Drake | The Deadly Years | Starfleet commodore and bureaucrat. Convenes an extraordinary competency hearing for Kirk, and subsequently assumes command of the Enterprise. |
| | Q-Less | Cousin of Quark and Rom. Bids 500 bars of gold-pressed latinum for a bejeweled dagger from the Gamma Quadrant during Vash's auction. |
| Percy Rodriguez | Court Martial | Starfleet commodore and commanding officer of Starbase 11. Convenes a court-martial of Kirk regarding the death of Lieutenant Commander Benjamin Finney. |
| Lawrence Montaigne | Amok Time | Vulcan; T'Pring's lover and Spock's rival for her affections. |
| Ken Jenkins | Evolution | Human astrophysicist. Tries to wipe out a race of nanites to further his own research. |
| James Sikking | SFS | Starfleet officer; captain of the USS Excelsior. |
| Lon Suder | Brad Dourif | Meld, Basics Part 1 & 2 | Betazoid Maquis brevet ensign. Helps retake Voyager after its commandeering by the Kazon. |
| Fintan McKeown | Fair Haven | Holographic character in Tom Paris's Fair Haven, owner of a pub in a quaint Irish village. Becomes romantically involved with Captain Janeway, who makes several modifications to his program. |
| Jacqueline Kim, Rihanne Quinn | GEN, STB | Ensign and pilot on the Enterprise-B; daughter of Hikaru Sulu. |
| Hikaru Sulu | George Takei, John Cho | TOS, TAS, TMP, WOK, SFS, TVH, TFF, TUC, GEN, Flashback, ST09, STID, STB | Helmsman of the USS Enterprise and Enterprise-A under Captain Kirk; Captain of the USS Excelsior. |
| Surak | Barry Atwater, Bruce Gray | The Savage Curtain, Awakening | Legendary Vulcan philosopher. |
| Jude Ciccolella | NEM | Romulan commander who assures Praetor Shinzon of the fleet's allegiance. |
| Steve Kehela | Fair Trade | Drug addict who buys his drugs at the Nekrit Supply Depot. |
| Laurence Luckinbill | TFF, The Serene Squall | Sarek's son by a Vulcan princess; Spock's half-brother. Hijacks the Enterprise-A in attempt to reach God at the center of the galaxy. |
| Michael Nouri | The Forge | Vulcan in possession of Surak's katra. Along with his followers, the Syrrannites, seeking the Kir'Shara, an ancient artifact containing Surak's original writings. Introduces himself as "Arev" to Jonathan Archer and T'Pol. |