Star Trek is a science fiction universe set in the distant future. Part of the appeal of the futuristic universe is the technological advancements that lead to healthcare changes. In the Star Trek universe, miracles can happen, and someone who dies may not stay dead thanks to technology.
While it's common to joke about red shirts dying on Star Trek, some major main characters have died on screen as well, and many of them have been resurrected. This shows the technological advancements while keeping important characters around for future storylines. Plus, it can lead to interesting new plot developments for the series.
11 Neelix (Voyager)
Neelix comes face to face with his own mortality in a surprisingly dark episode of Voyager. In the season four episode "Mortal Coil," Neelix is killed in a shuttle accident and brought back to life with Borg technology by Seven of Nine. Unfortunately, this also leads to a crisis of faith for Neelix.
Neelix had always believed in an afterlife, but after not experiencing anything (or at least not remembering experiencing anything), Neelix questions his own beliefs. This leads to him being suicidal, and the Voyager crew has to remind him of his importance to save his life.
10 Dr. Hugh Culber (Discovery)
Hugh Culber is the ship's doctor on Discovery. In season one, he is killed by crew member Ash Tyler, who was revealed to be a Klingon named Voq and was battling dueling personalities. But in season two, his consciousness was discovered hiding in a microscopic network allowing for him to be resurrected after his husband, Chief Engineer Stamets, built him a new body.
Culber's resurrection led to a unique look at PTSD from the perspective of a person who had died but had returned. It also provided a different look at the struggles Culber and Stamets were both going through, as Culber became reclusive and pushed Stamets away after returning from the dead.
9 Montgomery Scott (The Original Series)
This is one of the most shocking deaths of The Original Series. While the show hadn't shied away from killing crew members, they were usually either unknown red shirts or background characters that had only a few lines before their demise. This all changed when the Enterprise's Chief Engineer was killed by a space probe called Nomad.
The probe is under the impression that Kirk created Scotty, and offers to repair Scotty for him. Kirk, Dr. McCoy, and Nomad then go to sickbay, where Nomad resurrects Scotty. There are no lasting effects, and it's a blip on the radar overall, but it's still a shocking moment to hear McCoy say "He's dead, Jim," about Scotty. Amazingly, it was the second time a main character had been killed.
8 Dr. Leonard McCoy (The Original Series)
One season earlier, the ship's doctor, Leonard "Bones" McCoy, was killed on an away mission. During shore leave on a fantastical planet, Bones encountered someone who looked like the Black Knight from Arthurian legend. The good doctor was killed by the Knight's lance.
McCoy experienced a different resurrection because it wasn't a technological advancement that brought him back to life like Nomad did for Scotty. Instead, the planet's mysterious "keeper" decided to resurrect the doctor.
7 Harry Kim (Voyager)
Ensign Harry Kim holds the distinction of being the only Star Trek character to die no fewer than three times, and he came back each time. His first death came in season one of Voyager, when he wound up on a planet that an alien species used for a burial ground. Harry was resuscitated by the ship's doctor when he returned to the ship.
In the next season, a version of Harry from a different version of the ship was killed. This time, it was a hull breach that led to his death, but the main timeline Harry Kim was allowed to live. It would take three seasons before he would die again. This time, a Harry Kim from a different timeline accidentally destroys the ship. That version of Harry Kim sends a message through time to prevent the ship's destruction. The different timeline Harry dies, but the original version lives on.
6 Miles O' Brien (Deep Space Nine)
Miles O'Brien was the hard luck kid of Starfleet during his time on both The Next Generation and Deep Space Nine, but his several deaths in season three of DS9 may take the cake. After being exposed to radiation, O'Brien starts seeing glimpses of the future where he dies several times. He's eventually able to prevent all of these deaths.
Unfortunately, the original O'Brien still dies due to poisoning from the radiation, but his efforts to save his other lives allows him to continue on Deep Space Nine. A version of O'Brien who avoided death in the future takes over after the original succumbs to the radiation.
5 James Kirk (Generations; Into Darkness)
In the seventh Star Trek film, Kirk is taken to a Heaven-like nexus before returning to the real world, at the request of Jean-Luc Picard, years after he would have died naturally. This resurrection would be short-lived as he is killed by the villainous Soran.
In the Kelvin-verse Star Trek films, Kirk takes over Spock's story arc from the original universe. In Into Darkness, Kirk sacrifices himself to save his ship, before he is resurrected and completes the mission to stop Khan and Admiral Marcus.
4 Jean-Luc Picard (Picard)
Admiral Jean-Luc Picard died after the Borg DNA in his brain led to a case of Iurmodic Syndrome believed to be incurable. The DNA finally delivered the fatal moment during the first season of Picard, but Dr. Altan Soong wasn't ready to let the beloved Starfleet officer pass away.
Dr. Soong transferred Picard's memories and consciousness into a synthetic body that looked just like Jean-Luc Picard. The Admiral was allowed to live out the years he would have if the Borg DNA hadn't given him a terminal illness. This led to his organic body being a major plot point in season three of the show.
3 Tasha Yar (The Next Generation)
Tasha Yar's death in the first season of The Next Generation was the most meaningless of the franchise. Actress Denise Crosby wasn't happy with her character and asked to be written out of the show. She was killed in the first five minutes of an episode, and the show's creators used that episode to explore grief, especially in the context of Data's quest for humanity.
Her resurrection happens in an odd timeline where she never actually dies. The main timeline Yar never returns, but when a temporal anomaly takes the Enterprise into a different timeline, Yar is still alive and well aboard the ship from the past.
2 Data (Nemesis; Picard)
Data is an android who always brought about the questions of sentience and humanity. He wanted to experience everything human, including death. He sacrificed himself to save Picard at the end of Nemesis, although an earlier version of the android, called B-4, was brought back on board the Enterprise.
In the first season of Picard, data returns to say goodbye to Picard and seemingly die again. However, he would be brought back in season three. A new version of the android combining aspects of Data as well as B-4 and another brother android, Lore, as well as Dr. Soong's personality, led to a fight for control which Data wins, reuniting him with his friends.
1 Spock (The Wrath of Khan; The Search for Spock)
This is easily the most famous death and resurrection in all of Star Trek. Spock sacrifices himself to save the ship when Khan is leading an attack in The Wrath of Khan. His dying words serve as an inspiration for Star Trek fans to this day.
The third film featuring The Original Series cast revolves around Spock's resurrection. Spock transferred his katra to Dr. McCoy before sacrificing himself, and his body was sent to the Genesis planet where it was revived. His katra was restored and Spock was able to appear in three more The Original Series films and two Kelvinverse films.