A new species of the tardigrade genus Macrobiotus is described. The species, designated M. ciprianoi n.sp., was isolated from a mixture of Provence broom leaf litter and mosses, and from rock mossescollected in the Sierra de Guadarrama, Madrid (Spain). Given that Macrobiotus ciprianoi n. sp. sharesseveral characters to members of the ‘‘tenuis group’’, we assessed the taxonomic homogeneity of thegroup. The new species differs from those of the ‘‘tenuis group’’ according to a unique set ofcharacters related with claw shape, features of the buccal-pharyngeal apparatus, and egg morphology.Our analysis of holotypes and/or paratypes of ‘‘tenuis group’’ species and other Macrobiotus specieswith similar characters (M. bondavallii and M. caelicola) reflects the heterogeneity of this group ofspecies as currently described.