A new species of Tortricidae (Lepidoptera: Chlidanotinae: Polyorthini), Isotrias penedana sp. n., is described. The new species was collected in Serra da Peneda, in the Peneda-Gerês National Park located in the north-western region of Portugal. I. penedana differs from other species of the genus Isotrias by shape of the forewing and the male genitalia. In the new species forewing markings are completely atrophied or indistinct. The socii are short and broad, covered with long setae, and the costa of the valva is hardly concave basally. The imago and male genitalia are illustrated.
Isotrias penedana sp. n., Lepidoptera Tortricidae, Chlidanotinae, Polyorthini, new species, Portugal.