The Rythrian are a spacefaring species. They are known for being tall and for having ears that resemble loose flaps of skin.

In 2372, Benjamin Sisko and Quark encountered a Rythrian on Mephil Trantos who was working for the Orion Calculanthra. The Rythrian joined with a Skelarian in attacking Sisko, who was able to get out of the way of the Rythrians swing, causing the alien to hit his hand against the wall. While the Rythrian was distracted with the pain, Sisko was able to punch the Rythrian and knock him unconscious. The Rythrian late woke up and grabbed Sisko, although he dropped him when Quark aimed a phaser at the Rythrian and another at his Denebian associate. Sisko managed to hit the Rythrian again, causing the alien to miss his shot against Quark. Having incapacitated the Denebian, Quark shot the Rythrian. The Rythrian later revealed who he was working for to Sisko. (DS9 novel: Wrath of the Prophets)