Guinan from Star Trek: The Next Generation is from a race of extremely long-lived aliens, but how old is the mysterious bartender? Played by Whoopi Goldberg, Guinan was first introduced in season 2 of The Next Generation and went on to play a significant recurring role in the rest of the series. Along with tending the bar in Ten Forward, Guinan served as a confidant and informal counselor to many crew members on the USS Enterprise-D, most notably Captain Jean-Luc Picard with whom she shared a close, personal friendship.
Although human in appearance, it was revealed Guinan is actually a member of an alien race called the El-Aurians. Guinan's people are still something of a mystery in Star Trek canon; the name "El-Aurian" wasn't even given to the race until the film Star Trek: Generations. However, some significant El-Aurian traits and history have been explored thanks to Guinan. The species has been described as a race of "listeners", which explains Guinan's skill as a confidant to the crew. Additionally, the El-Aruian homeworld suffered a devastating attack by the Borg sometime around 2265, causing the destruction of their major cities and the assimilation of most of their population. Besides their listening abilities and history with the Borg, the most significant fact about El-Aurians is their extremely long lifespan, something fans have been interested in as it relates to Guinan.
Although Guinan's age has never been explicitly stated, context clues and outside source material can give a fairly accurate sense of how old she actually is. According to her profile on Startrek.com, Guinan is characterized as being "well over 600 years old". While this estimate seems fairly accurate for her current age, evidence from several episodes in TNG suggests Guinan was somewhere in the 500-year-old range when she was first introduced. The two-part episode "Time's Arrow", which depicted an adult Guinan on Earth in the year 1893, is the strongest evidence for this. The majority of "Time's Arrow" takes place 472 years before Guinan joined the crew of the Enterprise-D. From bits of information provided about Guinan's family, specifically her father, it appears El-Aurians' reach maturity by at least 100 years old, so if Guinan was around 100 in 1893, she would be in her 570s or 80s by the time she went to work on the Enterprise-D. TNG and its films only spanned fifteen years in the timeline, so by Star Trek: Nemesis Guinan would be at or approaching 600 years old, and in her 620s or 30s during Star Trek: Picard, where she is set to make an appearance in the upcoming season 2.
Guinan stated in the TNG episode "Rascals" that her father was 700 years old and in good health, which suggests the El-Aurian lifespan far exceeds 700 years. This gives a vague sense of just how long the race lives but also raises the question of whether or not they are immortal. There has been no concrete answer given to this question, but it has been shown that El-Aurains are vulnerable to death by injury or attack. This means El-Aurians are not immortal in the same way as a species like the Q, who truly cannot be killed except if they are stripped of their powers. Given the fact El-Aurians are more similar to other humanoid species than omnipotent beings like the Q, it is far more likely their long lives only seem like immortality and they will eventually age and die, albeit very slowly.
Whether or not audiences will get to see Whoopi Goldberg's Guinan age is another matter, although her upcoming return in Picard might provide a chance. Since Goldberg has aged since the last time she played the character, it is possible viewers might get to see an older version of Guinan in some context. Picard also has the chance to finally give fans an answer to the question of how old Guinan truly is, a question that was never satisfactorily answered on Star Trek: The Next Generation.