Abstract: Palaearctic populations of Myrmica ants so far known under the name M. scabrinodis Nylander, 1846 were studied by combining geometric morphometrics (GM) with nest-centroid (NC) clustering and hypothesis-driven data analysis. A new cryptic species, Myrmica martini sp.n., showing a rather limited geographical range extending over largely the montane to subalpine zones of the Pyrenees and French Alps, was identified. 41 landmarks and 252 semilandmarks were fixed in the clypeus, head capsule, mesosoma and petiole aspects of 359 ant workers belonging to 106 nest samples. Extracting the 14 most diagnostic shape components from a set of 316 relative warps and running these data in NCclustering, resulted in a complete species separation despite minute interspecific differences and large overlap in any character. The species identification provided by NC-Ward, NC-K-means and NMDS-K-Means clustering and by the controlling linear discriminant analysis agreed in each nest sample. There was no classification in disagreement with zoogeographic data. The lectotype samples of the five most similar and possibly synonymous taxa had near-to-zero probabilities of belonging to the M. martini sp.n. cluster: M. scabrinodis (p = 0.00015), M. scabrinodis var. rugulosoides Forel, 1915 (p = 0.0037), M. pilosiscapus Bondroit, 1920 (p = 0.0008), M. sabuleti var. spinosior Santschi, 1931 (p = 0.0006), and M. rolandi var. reticulata STÄRCKE, 1942 (p = 0.00001). Myrmica rolandi var. reticulata, of which a lectotype was designated here, is established as junior synonym of M. spinosior whereas M. scabrinodis var. rugulosoides and M. pilosiscapus are confirmed as junior synonyms of M. scabrinodis. We provide a rather simple system to discriminate M. martini from M. scabrinodis requiring 8 - 10 minutes of investigation time per specimen and resulting in an error of 3.6% on the nest sample level.