Parietaria semispeluncaria Yildirim, a new species endemic to eastern Anatolia, Turkey is described and illustrated. P. semispeluncaria Yildirim is most similar to P. rechingeri Chrtek from which it can be distinguished by stem, leaf, inflorescence and flower morphology. P. semispeluncaria is a perennial obligate chasmophyte that colonizes calcareous marlstone cliffs. It is known from a single locality in the Levent Canyon, Malatya Province. A species conservation assessment classifies P. semispeluncaria as 'Vulnerable' (VU) D1 + 2 on account of its restricted distribution.