Over the last 30 years, several mosquito- borne diseases have spread worldwide, threatening human and animal health, including lymphatic filariasis. Lymphatic filariasis is a major public health issue in tropical regions like Saudi Arabia, caused by parasitic worms. The parasitic worms Wuchereria bancrofti and Brugia malayi are transmitted by Culex quinquefasciatus. Cx. quinquefasciatus is a potential vector for various arboviruses like encephalitis virus and West Nile virus, along with protozoa like Plasmodium relictum that cause bird malaria. With the increasing number of mosquito species, there is an increased need for additional species identification. More attention is being directed to the immature stage, specifically the pupae, due to their valuable characteristics for species identification. Cx. quinquefaciatus, one of the nine Culicine species found in Saudi Arabia, lacks a complete description of its pupal stage and only has partial descriptions of other developmental stages, making identification challenging. This study aimed to investigate the morphological characteristics of Cx. quinquefaciatus pupae, focusing on the cephalothorax, trumpet, abdomen, paddle, and genital lobes, as well as the distribution and arrangement of setal branching and chaetotaxy. The pupae were collected from Qaryat Al Ulya Governorate, Eastern region, KSA, and maintained in a Biology Laboratory at the University of Hafr Al Batin from September to October 2022. The findings of this study have provided the essential characteristics regarding the distinguishing features of Cx. quinquefaciatus pupae to distinguish it from other closely related species. This identification could assist field entomologists in enhancing their efficiency by classifying mosquitoes during virus outbreaks.