The long-legged deep-sea lophogastrid, Eucopia sculpticauda Faxon, 1893, is reported for the first time from the Mariana Trench based on an adult female specimen collected at a depth of 7526 m. Our report significantly extends the recognized vertical distribution of the species into the hadal zone, and exceeds the greatest recorded depth for the order Lophogastrida. Additionally, cytochrome c oxidase I and 18S rRNA gene sequences of the Eucopia specimens from the Mariana Trench, Mid-Atlantic Ridge, west Atlantic Ocean, Gulf of Mexico and east Pacific Ocean were compared. We speculate that the low genetic divergence observed among individuals of E. sculpticauda from distant collecting locations could be correlated to its ontogenetic vertical migration behavior and strong swimming capability.