A new species of the genus Pycnogaster Graells, 1851 is described from Catalonia (Northeast of the Iberian Peninsula). Pycnogaster ribesiglesiasii n. sp. was collected in the Plana d’Ancosa in a calcicolous stepic scrub dominated mainly by thyme (Thymus vulgaris). L. ribesiglesiasii is compared to P. sanchezgomezi Bolívar, 1897 from which it can be separated mainly by the shape of the male cerci, the titillators and the male calling song. In addition, in the females by the protuberance of the seventh (7th) sclerite and the shape of subgenital plate.