Koloth is a recurring Klingon antagonist-turned-ally in the Star Trek franchise. He is one of the two main antagonists of the original series episode "The Trouble With Tribbles" (along with Arne Darvin), the main antagonist of the animated episode "More Tribbles, More Trouble" and a guest character in the Deep Space Nine episode "Blood Oath".
In his two live action appearances, he was portrayed by the late William Campbell, who also portrayed Trelane in "The Squire of Gothos". In his animated appearance, he was voiced by the late James Doohan, who also voiced Kor in "The Time Trap".
Koloth crossed paths with the Enterprise crew when he requested shore leave at Space Station K-7. The Federation officials were reluctant to allow Klingons on the station, which was storing the grain shipment about to be sent to the disputed Sherman's Planet, but could find no reason to refuse. When some of his crew ended up in a brawl with Enterprise officers, Koloth attempted to demand an apology from Kirk but was instead met with the fact that the Klingons had poisoned the grain. Ironically, Koloth and his crew's presence on the station indirectly led to the undercover Klingon agent responsible, Arne Darvin, being exposed, since tribbles reacted the same way to him as they did to the other Klingons. As a parting gift, the tribbles were beamed aboard Koloth's ship as he departed.
Koloth again find himself mixed up in tribble business when he was sent to recover the glommer, a genetically-engineered tribble-killing creature which had been stolen by the Federation trader Cyrano Jones. Kirk ended up reluctantly protecting Jones, resulting in a short battle between the Enterprise and Koloth's ship until the glommer was surrendered. However, Jones' tampering with the tribbles had caused them to become so large that the glommer's effectiveness was limited.
At some point, Koloth joined with two other Klingon officers Kang and Kor in order to defeat a group of pirates working for the Albino. They succeeded but the Albino escaped and, in revenge, infected the trio's first born sons with a virus which killed them. The three Klingons, together with Federation diplomat Curzon Dax, swore a blood oath to avenge the deaths.
Decades later, Kang summoned the other two to Deep Space 9, having got a lead on the Albino. Koloth was disgusted by Kor's fondness for drink and by the fact the new host for the Dax symbiont was a young woman, Jadzia. He wanted to exclude her from the mission and she responded by challenging him to a duel: Although he defeated her, she put up a good enough showing for him to accept her. Koloth was willing to go along with Kang's plan for an almost suicidal frontal assault on the Albino's base, but agreed to Dax disabling the guards' energy weapons, giving them the edge in hand-to-hand fighting. In the subsequent battle, the Albino and Kang killed each other, while Koloth was killed fighting the Albino's men.
The 1980s DC Star Trek comics depict Koloth as commanding a hidden Klingon space station from which he orders attack on Federation space. When the space station is exposed, Koloth activates the self-destruct rather than surrender and is apparently killed. This has not been reconciled with his reappearance in Deep Space 9.