In this paper, Allium tianmuense is described as a new species based on morphological and molecular analyses, and its taxonomic relationships are discussed. It grows in the understorey of deciduous broad-leaved forests at 1000‒1500 m a.s.l. in Tianmu Mountain in Zhejiang (southeast China). Morphological analysis indicates A. tianmuense should be classified into A. sect. Sacculiferum and is distinct from the common species A. thunbergii and A. chinense in the morphology of leaves, umbel, filaments and phenology. Nuclear ribosomal DNA internal transcribed spacer (ITS) phylogenetic analysis further confirmed the inclusion of A. tianmuense within A. sect. Sacculiferum and revealed its distinction from all other species of this section representing a new species.
