Abstract: Cycas chenii X. Gong & W. Zhou sp. nov., a new species of Cycas L., is described and illustrated here. The morphological and karyomorphological comparisons are made between C. chenii and the closely related taxa for defining its taxonomical status as a new species. Moreover, the phylogenetic position of C. chenii within 16Cycas species is determined using DNA sequences of two plastid regions, nuclear ribosomal internal transcribed spacers, and two nuclear regions. Cycas chenii is readily distinguished from the related C. guizhouensis K. M. Lan & R. F. Zou by an acaulescent stem. Phylogenetic evidence indicates that C. chenii is a distinct group related to C. guizhouensis in the Section Stangerioides. The distribution and conservation status of C. chenii are also discussed.

Key words: China, Cycas chenii, new species, phylogenetic position