Botanical explorations in the alpine zone of the Shahvar and Shah Kouh Mountains from Semnan and Golestan Provinces (northeastern Iran) led to the collection of interesting specimens of the genus Silene L. (Caryophyllaceae). Taxonomic study of these plants and comparison with determined plant specimens showed that the specimens belong to an unknown species. I describe it as S. aminiradii Gholipour, belonging to section Auriculatae (Boiss.) Schischk. from northeastern Iran. The new species is compared with S. lucida Chowdhuri and S. crispans Litv. as the most similar species. Silene aminiradii is a caespitose perennial alpine gynodioecious plant with prostrate stems covered with dense, retrorsely simple hairs. The distribution, ecological features, reproductive phenology, and photos of S. aminiradii are presented.