A new myxosporean parasite, Myxobolus stomum n. sp., is described from the oral cavity and lips of the blackspotted grunt Plectorhynicus gaterinus (Forsskal, 1775) in the Red Sea, Egypt. The parasite was observed as tiny aggregates of whitish cysts hardly noticed within the muscles of the oral cavity, especially within the lips. The spores were subspherical and measured 8.5x6.5 microm. Polar capsules were equal, pear-shaped, occupied about half of the spore length and measured 4.4x2.4 microm. Histological evaluation of the infection revealed no significant impact on the host. The ultrastructure of the plasmodial wall and sporogenesis of the present species followed the usual pattern valid for most studied myxosporean species.