Astragalus gigantirostratus, endemic to the E Elburs Mts, is described as a species new to science and illustrated. It is characterized by long fruits (7.5–11 cm), connate stipules, bifurcate hairs and a retuse wing petal. The new species belongs to A. sect. Cytisodes and is related to A. dolichocarpus, A. stenocarpus and A. pseudocytisoides. The hitherto known species of this section are all confined to the Turkestanian floristic province of the Irano-Turanian region. A. gigantirostratus thus constitutes an interesting range extension of this section into the Hyrcanian province.