A new saxicolous Orthotrichum species, O. dagestanicum sp. nov. is described from the southern part of Dagestan Republic (Eastern Caucasus). The combination of hyaline and serrulate leaf apices composed of elongate thick-walled cells, strongly 8-ribbed capsules, immersed stomata that are not strongly covered by subsidiary cells, and paired exostome teeth indicate its affinity to O. vittii F.Lara et al., endemic of Iberian Peninsula, and O. garretii Grout & Flowers from U.S.A., Utah. However, 8 non-appendiculate endostome segments differ it from both species.