The Kazon (/ˈkeɪzɒn/) are a fictional alien race in the Star Trek franchise. Developed by Star Trek: Voyager series' co-creators Rick Berman, Michael Piller, and Jeri Taylor, the Kazon serve as the primary antagonists during the show's first two seasons. They are represented as a nomadic species divided into eighteen separate sects, and characterized by their reliance on violence. A patriarchal society, the Kazon have a low opinion of women, and place pride in men becoming warriors and proving themselves in battle. The Kazon storylines frequently revolve around the attempts of Jal Culluh and his Kazon sect to steal technology from the USS Voyager, with the assistance of former Voyager ensign Seska. During the second season, the Voyager crew uncover more about the alien species' history and culture through a temporary truce. In their final major appearance, the Kazon successfully commandeer Voyager, but are eventually forced to surrender and retreat. The alien species have minor cameo appearances and references in the show's subsequent seasons, and have also been included in Star Trek Online and novels set in the Star Trek universe.

Inspired by gangs like the Crips and Bloods, the Kazon were seen by the show's co-creators as an apt metaphor for the fears and anxieties surrounding cities and gangs during the seasons' broadcast. The Kazon were developed as one of three new alien species that could be expanded as recurring antagonists. The other two were the Vidiians and the Sikarians. Michael Westmore was the primary make-up supervisor involved in the creation of the Kazon's appearance. Piller originally planned to cast young actors between the ages of eighteen and twenty-five exclusively, but decided to cast older and more experienced performers as they tested better during the audition process. Voyager's writing team dedicated a large portion of season two to the development of the alien species, with Piller writing a paper on them that would be used for the development of the Kazon-centric episodes. The Kazon were removed from the series following the season three premiere as the co-creators felt that their continued presence would strain the credibility of Voyager's journey home.

Critical response to the Kazon was generally negative. Some reviewers praised their ability to capture Voyager and maroon its crew on a desolate planet, while others felt they were poorly developed copies of Klingons and that the second season focused too much on them. The Kazon were included on several lists ranking the worst villains in Star Trek history, and were cited as an example of the racist implications in the franchise's alien species. During her re-watching of the series, TrekToday's Michelle Erica Green provided extensive criticism of the alien species, questioning the decision to feature them as the primary antagonists instead of the Vidiians, and Captain Kathryn Janeway's refusal to share technology with them. The Kazon were also poorly received by the show's cast members, who did not find them to be strong villains or compelling additions to the narrative.

The Kazon appear as the principal antagonists for Star Trek: Voyager's first two seasons. Introduced in the series premiere "Caretaker", they are shown as oppressors of the Ocampa, another alien race. The Ocampa Kes (Jennifer Lien) is first seen as a slave to the Kazon, and the Talaxian Neelix (Ethan Phillips) is revealed to have completed business deals with the alien species in the past. After seeing a display of the advanced technology on USS Voyager, specifically the replicator and transporter, the Kazon develop schemes to steal these machines and incorporate them into their own ships. Captain Kathryn Janeway (Kate Mulgrew) refuses to provide the hostile alien species with any information regarding Voyager's technology because of her fear of upsetting the power dynamics in the Delta Quadrant and thus violating the Prime Directive. Over subsequent episodes, the crew of the Maquis cell led by Chakotay (Robert Beltran)—which had been pursued by Voyager into the Delta Quadrant—merge with Voyager's Starfleet crew. In "State of Flux", the Voyager crew encounter Jal Culluh (Anthony De Longis), a Kazon sect leader and the series' primary Kazon character. In this episode, Voyager's ensign Seska (Martha Hackett) is revealed to be a Cardassian agent who had infiltrated Chakotay's Maquis cell, subsequently objecting to the merging of crews, and Janeway's refusal to violate the Prime Directive. Seska secretly funnels information to the Kazon in order to build an alliance with the alien species and expedite Voyager's journey home. After being caught while attempting to deliver replicator technology to the Kazon, Seska leaves Voyager to join them and becomes Culluh's lover and primary adviser.

During "Initiations", Chakotay becomes entangled with Kar (Aron Eisenberg), a young Kazon attempting to complete a rite of passage, and tries to act as a mentor for him. In "Maneuvers", Seska sets up a trap, resulting in the Kazon stealing a transporter module from Voyager. She advises Culluh to engineer the technology into the Kazon ships and use it to unite all Kazon sects with him as leader. Chakotay goes on a solo mission aiming to recover the technology, but is captured and tortured by Seska and Culluh. The Voyager crew rescue Chakotay, only to discover that Seska had extracted his DNA and used it to impregnate herself. Following this turn of events, Janeway attempts to form an alliance with the Kazon to secure safe passage through their area of space. During this process, the crew meet with the Trabe, an alien species who were persecuted by the Kazon following a violent feud. Janeway decides to ally with the Trabe and sets up a peace conference at the suggestion of Mabus (Charles O. Lucia), a Trabe leader. However, the Voyager crew discover that the Trabe mistreated the Kazon in the past and want to use the meeting as a trap to assassinate the Kazon leaders. Janeway stops the massacre from occurring, but relations between Voyager, the Kazon, and the other alien species in the Delta Quadrant are further strained as a result.

The Kazon make minor appearances in "Threshold", "Dreadnought", and "Lifesigns" as Seska helps them construct a plan to commandeer Voyager. In "Investigations", Neelix notices that one of the ship's crew is sending coded messages to the Kazon, and he uses his morning news program to track down the traitor. Tom Paris (Robert Duncan McNeill) helps Neelix by exhibiting poor and aggressive behavior to set up an appearance that he is willing to sabotage Voyager to elicit contact from the traitor. Neelix discovers that Michael Jonas (Raphael Sbarge), a Voyager crewmember who was formerly part of Chakotay's Marquis cell, is feeding Seska information regarding warp technology; Jonas is then killed in a fight with Neelix. The two-part episode "Basics" serves as the final major storyline for the Kazon in the series. Seska sends Voyager a distress call following the birth of her child and Culluh's discovery that he was not the father. Chakotay convinces Janeway and the rest of the crew to rescue Seska and his son from the Kazon, but they discover it is a trap to ambush Voyager. The Kazon takes control of the starship and maroons its crew on a seemingly desolate planet; The Doctor (Robert Picardo) and the troubled crewman Lon Suder (Brad Dourif) are the only two crew members left on board Voyager. The Doctor reveals to a disappointed Seska that Culluh, not Chakotay, is the father of her child. The Voyager crew retake the ship after Suder sacrifices himself to sabotage its phaser weapon systems. Seska is killed by an exploding console in the ensuing fight, and Culluh takes his child and leaves with the rest of the Kazon.

Even though the Kazon are not prominent beyond "Basics", they are referenced in subsequent seasons. In the fourth season, Seven of Nine (Jeri Ryan) reveals that the Borg never assimilate the Kazon, whom they refer to as species 329 and "unworthy of assimilation" due to a belief they would "detract from perfection". A Kazon crew member was included on a holographic reconstruction of Voyager as a warship. The Kazon also appear in both "Relativity" and "Shattered", which deal with time travel. In both episodes, characters visit the point at which Seska and the Kazon were in control of Voyager.

The Kazon are included in Star Trek Online, a massively multiplayer online role-playing game (MMORPG) developed by Cryptic Studios based on the Star Trek franchise. In the game, which is set in the 25th century, 30 years after the events of Star Trek: Nemesis, the sect Kazon-Nistrim is classified as a rising power after a new leader took control away from Culluh. He is identified as "hungry for power and eager to make a name for himself" and "more cunning and intelligent than most Kazon".