In October 2018, maize (Zea mays L.) leaf samples with symptoms commonly associated with tar spot were received from Hancock, Wyandot, Fulton, Clark, Van Wert, and Crawford Counties in Ohio. Disease severity on individual leaves ranged from <1 to 10%, depending on the hybrid and location. Lesions were black, raised, and rounded, and ranged in size from 0.9 to 3.93 mm by 0.72 to 2.0 mm (n = 40, average 2.28 by 1.38 mm). A few of the lesions (<1%) presented a tan halo surrounding the black spot, resembling the fisheye lesions often considered typical of tar spot. Microscopic observations of leaf pieces sectioned through lesions showed ascomata occurring singly or in groups within a clypeus. Ascomata contained cylindrical asci with hyaline, aseptate, ellipsoid ascospores, ranging in size from 5.0 to 7.5 by 7.5 to 13.75 µm (n = 40, average 5.9 by 10.9 µm), and filiform paraphyses. Based on symptoms and fungal morphology, the disease was identified as tar spot and the pathogen as Phyllachora maydis Maubl. For molecular confirmation, DNA was extracted from ascomata on leaf samples from Hancock County, and amplicons of the internal transcribed spacer regions were generated using primers ITS5 and ITS4 (White et al. 1990). The results confirmed the fungus as P. maydis, showing 97% sequence homology to GenBank deposit accession MG881848.1 (McCoy et al. 2018), with 100% query cover, max score of 830, and E value of 0.0. Because P. maydis is an obligate biotroph (Muller and Samuels 1984), and as such nonculturable (Ruhl et al. 2016), Koch’s postulates were not attempted. The sequence from Hancock County was deposited in GenBank (accession no. MK184990). Although previously reported in the United States in Indiana, Illinois, Florida, Iowa, Michigan, and Wisconsin (McCoy et al. 2018; Ruhl et al. 2016), tar spot is still an emerging disease in the United States for which the economic impact is unknown. However, there have been reports of significant yield loss in Illinois, Indiana, Michigan, and Wisconsin in 2018 (N. M. Kleczewski, personal communication). It has been suggested that significant losses occur in Central and South America when plants are coinfected with P. maydis and Monographella maydis (Mottaleb et al. 2018). The latter species has not been reported in the United States, but evidence from preliminary studies indicates that P. maydis alone may be capable of impacting grain yield (N. M. Kleczewski, personal communication).