As a result of our taxonomic studies of Astragalus L. sect. Hymenostegis Bunge, we recognize nine new species of this genus from Zanjan Province in northwestern Iran, namely: A. atrokurdicus Maassoumi, F. Ghahrem., Bagheri & Podlech, A. austrotaromensis Maassoumi, F. Ghahrem., Bagheri & Podlech, A. dejectus Maassoumi, F. Ghahrem. & Bagheri, A. mostafa-assadii Bagheri, Maassoumi, F. Ghahrem. & Podlech, A. paralurgiformis F. Ghahrem., Maassoumi & Bagheri, A. pluriflorus F. Ghahrem., Maassoumi, Bagheri & Podlech, A. pseudoparalurges F. Ghahrem., Maassoumi, Bagheri & Podlech, A. sohrevardianus Bagheri, Maassoumi & F. Ghahrem., and A. sublaguriformis Bagheri, Maassoumi & F. Ghahrem., which are described and illustrated here. The new species are also compared with the taxa that are morphologically most similar and presumed to be closely related.