Guinan /ˈɡaɪnən/ is a recurring character in the Star Trek franchise, portrayed by American actress Whoopi Goldberg. The character first appeared in the television series Star Trek: The Next Generation in 1988 and went on to appear in the films Star Trek Generations and Star Trek: Nemesis as well as the television series Star Trek: Picard. She was also played as a child by Isis Carmen Jones in the episode "Rascals" and a younger version of the character by Ito Aghayere in Picard.

Guinan is a bartender and attached counselor in the Ten-Forward lounge aboard the starship USS Enterprise-D. The character first appears in the second-season opening episode "The Child", and makes recurring appearances during the next four seasons. Guinan was partly inspired by the Star Wars character Yoda, and is said to be hundreds of years old with corresponding wisdom and insight which she often uses to defuse difficult situations or comfort other characters.

Following the departure of Denise Crosby from the role of Tasha Yar during the first season of Star Trek: The Next Generation, established actress Whoopi Goldberg believed there was a vacancy for a female actress on the series. She had been a lifelong fan of Star Trek, having been inspired to become an actress by Nichelle Nichols' appearances as Uhura in The Original Series. Goldberg later recalled that she first saw an episode of the series in her youth and after Uhura appeared on-screen, she went running through her house shouting "Come here, mom, everybody, come quick, come quick, there's a black lady on television and she ain't no maid!" Goldberg approached her friend LeVar Burton, who played Geordi La Forge in The Next Generation, but the producers of the series ignored her, by one account believing they were being pranked until Goldberg telephoned the production office directly. However, executive producer Rick Berman later recalled it was Goldberg's manager who made the call, inviting him and series creator Gene Roddenberry out to lunch with Goldberg to discuss her appearing on the series.

At the time, plans were already underway to add a lounge set to the series. Named Ten-Forward, it was created to have a setting where the crew of the USS Enterprise-D could be shown interacting with each other as well as various aliens in a more casual setting. At the lunch between Berman, Roddenberry and Goldberg, she explained that Star Trek was the only futuristic science fiction series at the time she knew of that featured black people prominently. She asked whether they had already cast the new Doctor, following the firing of Gates McFadden from the role of Beverly Crusher. Roddenberry and Berman instead suggested the creation of a new character specifically for Goldberg. Goldberg was unable to commit to appearing as a permanent member of the cast, which fit in with plans for Ten-Forward as they were not expecting the lounge to appear in every episode.

The character of Guinan was based on Mary Louise Cecilia "Texas" Guinan, a prohibition-era emcee and owner of the 300 Club in New York City. While the name was adopted, the characterization was changed to a worldly mystic, in line with Yoda from the Star Wars franchise. Gene Roddenberry, the creator of Star Trek, had envisaged the character Guinan as extremely old, leading Goldberg to suggest that she could be the ancestor of some of the other characters on the series.

When Goldberg made her first appearance as Guinan, in the episode "The Child", she was credited as a "Special Guest Star" alongside Diana Muldaur who appeared throughout the second season as Doctor Katherine Pulaski. Guinan-centric episodes were scheduled throughout the rest of the run of The Next Generation to coincide with the availability of Goldberg, who at the time was continuing to appear in films and other work. In one instance, for "Imaginary Friend", Guinan was written in at short notice, taking lines intended for other characters after Goldberg unexpectedly became available.

There were plans to introduce a son of Guinan at some point in The Next Generation, but this never occurred. The idea was resurrected during the writing process of the Star Trek: Deep Space Nine episode "Rivals", with the character of Martus Mazur intended to be Guinan's son. After Goldberg was unable to make a guest appearance, the relationship between the two characters was written out. However, the first time that the El-Aurian species was mentioned by name was in this episode, but this may have been inspired by the scripts for Star Trek Generations which the writing team would have seen by that point in the production of the series.

Goldberg became a personal friend of creator Gene Roddenberry, subsequently being one of the eulogists at his funeral in 1991. During the initial production of Star Trek VI: The Undiscovered Country, she met with director Nicholas Meyer to discuss appearing as a Klingon in the film. This was vetoed by actor Leonard Nimoy, who had taken the lead on arrangements for the film, as with Christian Slater already set to appear in the film he did not want to be overwhelmed with celebrity cameos. She later described Guinan as a combination of Yoda, herself and Andrei Sakharov, adding that she was "more grateful for Star Trek now as a mother and grandmother" and described the prospect of Star Trek, saying "We all need to believe there is a good, positive future for us."