The Lissepians were a humanoid species native to Lissepia, and were frequent visitors to Deep Space 9. During the 24th century, the Lissepians were active trade partners with the Cardassians, because they were noted for always paying their bills. Lissepians were often used as intermediaries between the Cardassians and their colonies in the Demilitarized Zone following its creation in 2370. The Lissepians, however, were caught more often than their fellow Cardassian intermediaries, the Xepolites. (DS9: "The Homecoming", "The Maquis, Part II")
In 2365, while the entire planet of Lissepia was celebrating Mother's Day, five thieves broke into the Central Bank of Lissepia and stole one thousand bricks of gold-pressed latinum in what became known as the Lissepian Mother's Day Heist. Morn was one of five thieves who stole the thousand bricks, later depositing the gold in the Bank of Bolias and hiding the latinum in his second stomach. After the statute of limitations ran out in 2374, Morn faked his own death to throw his partners off his trail. (DS9: "Who Mourns for Morn?")
In 2370, while traveling to Cardassia IV, Chief Miles O'Brien and Major Kira Nerys successfully bluffed their way into Cardassian space by disguising their runabout Rio Grande as the Lissepian transport Martuk. They were scanned by a Cardassian navigational control post, which recognized that the ship's subspace field emitters were malfunctioning and offered assistance. In fear of getting caught, Major Kira quickly covered with the explanation that they were hauling a shipment of high-priority rulot seeds to Gul Marayn on Cardassia IV, and at the risk of ruining the crops they would deny help and make the repairs following their delivery. (DS9: "The Homecoming")
In 2372, Quark purchased a program from a Lissepian that allowed him to run holographic waiters in his bar while Rom and the rest of his wait staff were on strike. Unfortunately, the Lissepian neglected to inform Quark that certain energy sources could interfere with the imaging system. (DS9: "Bar Association")
- No Lissepian characters were ever assigned names in canon productions.