- "Oh, she's so... she's so beautiful. Kes. I think one day she'll see the sun."
- —Martis after the birth of Kes, 2369 [src]
Kes was an Ocampa female born in 2369. Kes was a curious person who was eager to explore her planet Ocampa V beyond the subterranean city and to not be dependent on the Caretaker. After emerging on the surface of her world she was taken prisoner by the Kazon and began a relationship with the Talaxian trader, Neelix.
Both Kes and Neelix' life changed in 2371, when they were rescued by the USS Voyager, a Federation starship stranded over 70,000 light years from Earth. Within days, Kes suggested, and Janeway tasked her with, coverting a cargo bay into an airponics bay to help Voyager conserve resources. (VOY episode: "Parallax") She soon found herself a role aboard Voyager as The Doctor's assistant. Her growing telepathic powers also helped to save the ship and crew on several occasions.
Species 8472, telepathic aliens from 'fluidic space', a different universe with different physical laws, contacted Kes telepathically during their conflict with the Borg, and Kes told the captain that it was them and not the Borg that they should be worried about, which was crucial in Janeway's decision to temporarily ally with the Borg against them. (VOY episode: "Scorpion") While allied with them, we learn that the Borg started the war by invading fluidic space, and later we learn that Species 8472 was planning to infiltrate Starfleet, but only out of concern that humans might be planning an invasion of their own, and Janeway is able to convince them otherwise. (VOY episode: "In the Flesh")
Allying with the Borg was a controversial decision, which Commander Chakotay was against, and so timelines exist in which this does not occur. (Infinity's Prism - Myriad Universes short story: "Places of Exile") In the short story Places of Exile we learn that our universe branches off into an infinity of timelines due to these kinds of choices but that this does not occur in fluidic space. This was one reason that species 8472 was so concerned about potential invasions and wars with species from our universe. In one timeline in which Chakotay was able to dissuade Janeway from the alliance with the Borg, they learn all this, with Kes playing a major role as both a medical scientist and as a diplomat. We also learn that it was the telepathic contact with Species 8472 (or Groundskeepers, as they preferred to be called, after their diplomat took the form of Groundskeeper Boothby from Starfleet Academy) that triggered the expansion of her telepathic and telekinetic powers, which in the original timeline led to her departing Voyager.
By 2376, Kes' powers had failed and she returned to Voyager to reap revenge on her former crewmates. However, a meeting with her past self convinced her that the Voyager crew were her friends and she returned home to Ocampa to help her people. (VOY episode: "Fury")
Once back on Ocampa on stardate 54868.6 in 2377, Kes implanted her lifetime's memories into a childhood friend's son's mind and used her newly-returned powers to regenerate Ocampa's energies, returning the planet to a blissful long-term state, but killing Kes in the process. (VOY - Strange New Worlds V short story: "Restoration")
- This is in contradiction with the Voyager novel String Theory: Evolution. In the String Theory trilogy, Kes was called to Ocampa's distant past to help the Doctor and Q oversee the birth of an Ocampa/Nacene hybrid; the Ocampan mother lacked the life energy to carry the child to term, so her life-force merged with Kes', who then mated with the Nacene male. It was also revealed that the Kes who attacked Voyager in "Fury" was not actually the future Kes, but was instead the personification of the anger and rage in Kes' soul, created when she was forced to separate herself from the Ocampan she had merged with while fighting a rogue Nacene. As a result of the improper separation, Kes' 'dark side' merged with the body of the Ocampan, although the spirit of the Ocampan herself passed on peacefully. After a short pregnancy, Kes' son Balim was born, and then taken to be raised safely by Q, protected from other Nacene who would wish to harm him. Returning to the present day and reuniting with the now-fully grown Balim, Kes returned to Ocampa, and was witness to Balim's restoration of the planet's biosphere. Therefore we can assume that Kes survived the events in "Restoration".