Myxobolus sp. (Myxozoa: Myxosporea) was recovered from gill tissues of the Nile fish Labeo niloticus at Assiut locality, Egypt. Mature spores were elliptical in shape, with two equal polar capsules situated anteriorly  and occupied nearly more than half length of the spores. Each spore measured 10.4-14.0 mm in length and 8.0-11.3 mm in width. Polar capsules were 5.5 – 7.3 mm in length and 3.5-4.5 mm in width. They occupied nearly more than half length of spores. Semi-thin-sections revealed that the plasmodium was surrounded by an outer wall of the host origin and inner wall of the parasite and contained numerous spores at different stages of development. Cytochemical studies showed that the spores and sporoblasts contained large amount of glycogen and protein. Best's carmine stain showed the presence of iodinophilous vacuoles in the sporoplasm of spores as a rounded structure. Scanning electron microscope revealed the smooth nature of the spore valve surface. The polar capsules, shell valves and sutural ridge line are represented by anterior and posterior grooves. The transmission electron microscope revealed that the mature spores have two valves arising from the valvogenic cells and joined by the sutural line.