The biodiversity of deep-sea hydrothermal vents in the Indian Ocean remains poorly characterised compared with that of their Pacific and Atlantic counterparts. Although the Longqi hydrothermal vent field is the most extensively explored vent site on the ultra-slow-spreading Southwest Indian Ridge, it is still a source of new discoveries. Here, we report and formally describe a new peltospirid snail from Longqi - Lirapex felix sp. nov. Known from only two specimens, it differs from other named Lirapex species by a depressed spire and the lack of coil loosening on the body whorl. Examinations of the external anatomy and radular characteristics agree with its placement in Lirapex, which is also supported by a molecular phylogeny reconstructed using the barcoding fragment of the mitochondrial cytochrome c oxidase I (COI) gene. This is the fifth peltospirid snail known to inhabit the Longqi field, three of which (including Lirapex felix sp. nov.) have been found nowhere else. There is growing evidence that the Longqi field represents a biogeographically unique site among Indian Ocean vents. The discovery of Lirapex felix sp. nov. adds to the unique biodiversity of Longqi field, with implications for conservation in the light of potential deep-sea mining. This work is registered in ZooBank under: urn:lsid:zoobank.org:pub:3B892762-2110-4A1E-A80D-1779CBEC5EB3