Twenty species of Culex of the subgenus Culex are recognized in southwestern Asia and Egypt: pipiens Linnaeus, quinquefasciatus Say, vagans Wiedemann, torrentium Martini, decens Theobald, antennatus (Becker), univittatus Theobald, perexiguus Theobald, theileri Theobald, laticinctus Edwards, mattinglyi Knight, simpsoni Theobald, sinaiticus Kirkpatrick, duttoni Theobald, sitiens Wiedemann, poicilipes (Theobald), mimeticus Noe, bitaeniorhynchus Giles, tritaeniorhynchus Giles, and pseudovishnui Colless. Keys, descriptions, and illustrations are provided for the identification of the adult, pupal, and larval stages of each species. Keys are also included for the genera of mosquitoes and the subgenera of Culex occurring in the region. The individual treatment of each species also includes a complete synonymy, a summary of previous literature, a systematic discussion, information on bionomics and distribution, and a synopsis of material examined. Lectotype specimens are designated for decens, simpsoni, duttoni, and 16 junior synonyms. A neotype specimen is designated for bitaeniorhynchus. Six new junior synonyms are recognized: alpha Seguy (= theileri); calloti Rioux and Pech, erectus Iglisch, and torridus Iglisch (= pipiens); ethiopicus Edwards (= bitaeniorhynchus); and mauritanicus Callot (= simpsoni). The recognized species are arranged into three groups and 10 subgroups. The duttoni group and the decens and simpsoni subgroups are recognized for the first time.