The Borg are one of Star Trek's most iconic villains and have made many appearances in the franchise since their introduction. Although the Borg were created as a second-choice villain for Star Trek: The Next Generation after the Ferengi failed to resonate with audiences, they more than made up for the Ferengi's shortcomings and became one of the most terrifying adversaries in Star Trek history. A cybernetic, hive-mind species whose only goal was to assimilate as many people as possible into perpetual slavery in their collective, the Borg were immediately the stuff of nightmares for the Federation.
The Borg first came into with Captain Jean-Luc Picard (Patrick Stewart) and the crew of the USS Enterprise-D after Q (John de Lancie) flung them across the galaxy to teach them a lesson about just what kind of dangers they faced in space. After encountering the Enterprise-D, the Borg made it their mission to assimilate all of Starfleet for the betterment of their collective and demonstrated just how powerful they were in TNG episodes like "The Best of Both Worlds Parts I and II". Luckily, after TNG ended, Star Trek continued to bring the Borg back as antagonists in other shows and movies.
1 Star Trek: The Next Generation
Given how popular they became, it is surprising that the Borg only appeared in six episodes of Star Trek: The Next Generation. However, their appearances left a lasting effect on the franchise. Besides episodes like "Q Who" and "The Best of Both Worlds" which introduced the Borg and demonstrated just how formidable an adversary they were, TNG also began to explore the trauma that individuals taken by the Collective faced during and after assimilation. This was done mostly through Captain Picard, who was assimilated and briefly became Locutus of Borg, something that shaped his storylines for decades to come.
Star Trek: TNG's other memorable Borg character was Hugh (Jonathan Del Arco), a drone rescued by the Enterprise-D who began to regain his individuality when he was separated from the Collective. Hugh helped Picard grapple with his prejudice against the Borg and was the first example of a completely assimilated drone being rehabilitated, offering the audience a glimpse into the fact that many Borg drones were victims of the Collective rather than willing participants. Although Hugh was forced to return to the Borg, he did eventually escape and his story was explored further in Star Trek: Picard.
2 Star Trek: First
Star Trek: First was the second franchise film starring the cast of TNG, and featured the Borg as its main antagonists. The plot revolved around Captain Picard and crew traveling back in time to stop the Borg from assimilating Earth in the past and thus preventing the birth of the Federation. Star Trek: First was also the first project to introduce the Borg Queen (Alice Krige) as the Collective's leader, a decision that proved somewhat controversial. Despite First retconning her into existence, the Borg Queen went on to have extensive appearances in the rest of the franchise and has become an important part of Star Trek lore.
3 Star Trek: Voyager
To date, Star Trek: Voyager is the series in which the Borg have made the most appearances, 23 episodes in total. Given that Voyager was set in the Delta Quadrant, the region of space where the Borg originated, their inclusion in the show only made sense. The Borg served as the main villains on Voyager from seasons 4-7 and were instrumental in the series finale where they unwittingly helped the crew return home. The journey of a drone regaining their humanity after being separated from the Collective was also once again explored through Seven of Nine (Jeri Ryan).
4 Star Trek: Enterprise
Although Star Trek: Enterprise was set well before TNG in the timeline, the show still found a way to include the Borg. Season 2, episode 23, "Regeneration" featured the crew of the Enterprise NX-01 battling the two drones, part of the groups that had traveled back in time during First . After being revived by an unwitting research team in the Arctic, the Borg attempted to escape back to the Collective. Captain Jonathan Archer (Scott Bakula) and the rest of Enterprise's crew were able to stop the drones, but the episode ended foreshadowing the Borg's 24th-century conflict with the Federation after a message was transmitted to the Delta Quadrant.
5 Star Trek: Picard
Given Jean-Luc Picard's history, it isn't surprising that the Borg played a major role in all three seasons of Star Trek: Picard. Picard season 1 delved deeper into the plight of xBs, former Borg drones who had escaped the Collective, and reintroduced Seven of Nine to the franchise. Season 2 provided a significant update to the Borg with the development of a new Collective under the guidance of Agnes Jurati (Alison Pill), who had merged with a version of the Borg Queen from an alternate timeline and convinced her to help create a new species of Borg that agreed to act as allies to the Federation rather than enemies.
Star Trek: Picard season 3, however, included arguably the most important Borg-related plot. After suffering a massive defeat in the finale of Star Trek: Voyager, the original Borg Queen intended on taking one final stand against the Federation and briefly managed to assimilate much of Starfleet with the help of iral Picard's DNA and his son, Jack Crusher (Ed Speleers). However, Picard and the Enterprise-D crew were able to rescue Jack and destroy the last remaining Borg cube, killing the Queen and effectively ending the Borg's reign of terror in the franchise, given that the only Borg remaining are Jurati's Collective.
6 Star Trek: Lower Decks
Star Trek: Lower Decks has featured the Borg in five episodes, but in three out of those five, the Collective was only holograms. Since Lower Decks is mostly a comedy and tends to poke fun and established Star Trek concepts, it's not surprising that the episodes featuring the Borg have used them in a humorous manner. The most Borg-heavy episode, season 2, episode 8, "I, Excretus", dealt with Ensign Brad Boimler (Jack Quaid) briefly becoming trapped in a Borg training simulation in which he was determined to get a perfect score. However, the episode did feature the return of Alice Krige as the Borg Queen, a great callback for viewers.
7 Star Trek: Prodigy
Star Trek: Prodigy has only had one episode that included the Borg so far. In Prodigy season 1, episode 12, "Let Sleeping Borg Lie", the crew of the USS Protostar encountered a Borg cube which they infiltrated to try and find information on how to disable the Living Construct. However, the episode almost ended with the whole crew assimilated by the Borg after Zero (Angus Imrie) allowed themself to be taken over by the Collective in hopes of obtaining the information. While Star Trek's Borg didn't play a huge part in Prodigy's story overall, they certainly left a lasting first impression on the Protostar's crew.