Adult worms of Rhadinorhynchus dorsoventrospinosus (Acanthocephala: Rhadinor-hynchidae) were collected from the small intestine of the red spot emperor Lethrinus lentjan (family Lethrinidae) from locations along the Red Sea at Jeddah City, Saudi Arabia. Twenty three out of 70 fish specimens (32.9%) were found to be naturally infected. The parasite was described using photo research Zeiss microscopy and a scanning electron microscope (SEM). Light microscopic studies revealed that the adult worm possessed a proboscis which was long, cylindrical with a uniform width measured 0.44±0.02 (0.38-0.46) mm in length and 0.12±0.02 (0.09-0.15) mm in width. Proboscis hooks observed by scanning electron microscopy were large, uniform in size (14-16 rows of 26 hooks each) with a row of longer hooks at the base. Comparison between the present described species and four species of the same genus was done, it was observed that there was only one comparable species, R. dorsoventrospinosus resembled the present parasite in the general morphology and differed from others, so the present studied species is classified as R. dorsoventrospinosus with new host and locality records.