Greynax was a Klingon who lived during the 23rd century. A former soldier of the Klingon Empire, he joined the Broken Circle mining syndicate on Cajitar IV following the end of the Federation-Klingon War in 2257. He and his compatriots spoke Kach-Ugh, an obsure dialect of Klingonese.
In 2259, Lieutenant La'an Noonien-Singh of the USS Enterprise, disguised as an arms dealer, arranged to meet Greynax through Lukata, ostensibly to sell him Starfleet type 2 phasers. During the meeting, Greynax was incensed that Noonien-Singh had barely half of the two dozen phasers she agreed to provide, yet insisted on charging double. When he threatened violence, Noonien-Singh bluffed him by threatening them all with an "antimatter detonation switch". Impressed, Greynax accepted her deal, but told her that he needed more. (SNW: "The Broken Circle")
Greynax was played by Alex Spencer.