Iris series Tenuifoliae (Diels) G.H.M.Lawr., which is widely distributed across Central and East Asia, comprises approximately 10 recognized taxa. However, taxonomic boundaries and phylogenetic relationships within the series have remained ambiguous due to considerable morphological complexity and insufficient molecular evidence. To resolve this, we conducted an integrated study using complete chloroplast genome sequences and morphological data. Our results clearly delineate the series's boundaries and establish its phylogenetic position within the genus Iris. The series was resolved into three strongly supported clades, with the circumscription of one clade corroborated by a specific inversion in the Small Single-Copy (SSC) region of the chloroplast genome. Furthermore, we describe 3 new species from central-western China: Iris liupanshanensis H.T.Li, Z.Z.Zhang & T.Y.Zuo, sp. nov., Iris helanshanensis Z.Z.Zhang, T.Y.Zuo & H.T.Li, sp. nov. and Iris coeruleoviridis T.Y.Zuo, H.T.Li & Z.Z.Zhang, sp. nov.