Mystus cineraceus, new species, is described from the Irrawaddy River drainage in northern Myanmar. It is distinguished from congeners in having a unique combination of a long-based adipose fin (40.9–45.9% SL) that contacts the base of the last dorsal-fin ray anteriorly, a color pattern consisting of a uniform brownish-gray body with a diffuse dark midlateral line and a diffusely dark tympanic region (very indistinct in some individuals), 13–15 rakers on the first gill arch, dorsal-fin spine length 10.9–13.4% SL, body depth at anus 20.7–23.4% SL, head length 24.1–27.2% SL, maxillary barbel reaching to middle of anal-fin base (247.4–345.0% HL), absence of a black spot at the base of the dorsal-fin spine and at the base of the caudal fin, and cranial fontanel reaching the base of the supraoccipital spine. The issues surrounding the identification of M. bleekeri, a species from India similar to M. cineraceus, are also discussed.