• conservation status;
  • determination key;
  • geographical distribution;
  • systematic revision;
  • taxonomic description

Stachys is a large and taxonomically complex genus of Lamiaceae (Lamioideae: Stachydeae). On the basis of morphological examination and field investigation, we revised the genus Stachys in Iran. We examined about 3500 specimens from various herbaria and produced a key for identification of all taxa found in Iran. The following are provided for each taxon: a description along with the complete synonymy, notes on nomenclature and relationships within the genus, geographical distribution, habitat, IUCN conservation status assessment and selected materials examined. The following taxa are reported here as new for Iran: S. atherocalyx, S. kotschyi, S. melampyroides and S. recta subsp. subcrenata. Several taxa are placed in synonymy for the first time here: S. persica is a synonym of S. alpina, S. koelzii is a synonym of S. aucheri, S. ballotiformis is a synonym of S. kurdica subsp. kurdica, and S. setifera subsp. daenensis and S. setifera subsp. iranica are synonyms of S. setifera. Two taxa are reduced to the rank of subspecies: S. kurdica subsp. asterocalyx and S. pilifera subsp. ixodes. According to the present revision, the genus contains 32 species, nine subspecies and two hybrids in Iran with 17 endemic taxa. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 573–617.