New faunistic and taxonomic data are provided for 19 families of Iranian spiders. Stemonyphantes arta Esyunin et Zamani, sp. nov. (Linyphiidae) is described from a male and a female collected in the Zanjan Province. Five genera of the family Theridiidae (Pholcomma, Phoroncidia, Phycosoma, Rhomphaea and Rugathodes) and 21 species are recorded from Iran for the first time, and 119 new province records are provided for 51 species. Additionally, Megarctosa bamiana Roewer, 1960 (Lycosidae) is transferred to the genus Arctosa C.L. Koch, 1847. A mistake in the original description of Gnaphosa azerbaidzhanica Tuneva et Esyunin, 2003 (Gnaphosidae), namely a mismatch of the figures of this species with those of G. tigrina Simon, 1878, is discussed and corrected here. Considering the results presented in this paper, the total number of spiders recorded from Iran is raised to 888 species in 321 genera.