Praniza larvae of Gnathia sp. were reported on the gills of 18 Iraqi sea fish species. Hosts were eight elasmobranchs and 10 teleosts. Cartilaginous hosts belong to four families, with highest mean prevalence was 100% in Pastinachus sephen, while the lowest prevalence was 25% in Gymnura poecilura. Teleost hosts belong to seven families, the highest prevalence was 50% in Rabdosargus haffara and the lowest was 1.6% in Tenualosa ilisha. The higher mean intensity of infection was 12.3 in Chiloscyllium arabicum, and only one in all teleost fish species. Praniza parasite of C. arabicum has long body, concave cephalon, narrowing anteriorly with truncate frontal margin, the compound eyes large, pleotelson triangular, uropods have endopods not extending beyond the end of the pleotelson. [ABSTRACT FROM AUTHOR]