In May 2019, approximately 30% of 372 yellow ginger (Dioscorea zingiberensis C. H. Wright) plants in six fields of Nanjing Botanical Garden (3114'N, 11822'E) showed 3 to 12 mm-wide black leaf spots. The fungus was isolated from symptomatic tissues, previously surface-disinfected with 1% sodium hypochlorite for 2 min, triple rinsed with sterile water, and plated on potato dextrose agar (PDA). The colonies were greyish-green or brown-yellow with whitish margins after 5 days of incubation at 25 °C. Conidia were obpyriform to ellipsoid, dark brown, septate, with 1–8 transverse and 0–3 longitudinal septa, with 11.2–48.5 × 4.5–12.3 µm in size (n = 50). The fungus resembled Alternaria spp. morphologically (Simmons 2007). The ribosomal internal transcribed spacer (ITS) region, plasma membrane ATPase (ATP) gene, and calmodulin (CAL) gene were amplified using primers ITS1/ITS4, ATPDF1/ATPDR1, and CALDF1/CALDR1, respectively (Lawrence et al. 2013). The consensus sequences of ITS, ATP and CAL (GenBank Accession Nos. MK560480, MT416124 and MT416125, respectively) from a representative isolate SY-4 showed 100%, 99.58% and 98.85% similarity with Alternaria tenuissima (Kunze) Wiltshire (KX015987, JQ671875 and JQ646209, respectively), and phylogenetic analysis confirmed the fungus identity. Ten leaves from each of three 1-month-old of D. zingiberensis plants were inoculated with 5-mm mycelial plugs, and kept at 25 °C with a 12-hour photoperiod. Sterilized PDA plugs were used as controls. Black spots similar to those observed in the field were visible on all the inoculated leaves after 3 days, whereas no symptoms on the controls. A. tenuissima was only reisolated from all symptomatic leaves, fulfilling Koch’s postulates. Although A. tenuissima has been reported to cause blight disease on Chinese yam (Dioscorea polystachya Turczaninow) in China, this is the first report of A. tenuissima causing leaf spot on D. zingiberensis in China and worldwide (Farr and Rossman 2022). Therefore, other yam varieties (Dioscorea spp.) may be threatened.