A new histozoic species of myxosporidian, Myxosoma microspora n.sp., infecting the gill filaments of Mugil cephalus is described. Cysts measuring 0.5–1.0 mm in diameter were found attached to the gill filaments. Spherical or slightly oval, spores 4.8–5.2 μm in diameter, were present and possessed a thin outer mucous envelope which appeared as small conical protuberances at the ends of the equatorial axis. Polar capsules were pyriform in shape, equal in size and measured 1.6–2.0 × 1.0–1.2 μm; the polar filaments were 22–28 μm in length. There was a bean-shaped sporoplasm measuring 3.5 × 1.5 μm. No iodine vacuole was detected when the parasite was stained with Lugol's iodine.