We have found that a taxon usually identified as A. kendevani Forster, 1956 is represented in the Elburz Mts., N. Iran by two reproductively isolated groups of butterflies that are morphologically very similar and fly in Shahkuh in the eastern part of the Elburz Mts., syntopically and synchronously. In Shahkuh these groups have different chromosome numbers, n=15 and n=16. They also differ from one another by 10 fixed nucleotide substitutions in a 448 bp fragment of the mitochondrial COI gene and form discrete clusters in neighbour-joining and maximum parsimony trees. Analysis of morphological, molecular and chromosomal data, field observations and study of type and historical material in museums of Munich, Berlin, Paris and London showed that one of these groups is represented by known taxa, A. kendevani kendevani Forster, 1956 (Central Elburz) and A. kendevani pseudoxerxes Forster, 1956 (East Elburz). Another group is described here as Agrodiaetus shahkuhensis sp.n. The new species is genetically very distan