Illustrated keys for the identification of the fourth-instar larvae and adult females of the mosquito genera Culex and Lutzia is presented, along with information on the geographic distribution of each species, and bionomics. Eighty-two species belonging to subgenera Culex, Culiciomyia, Eumelanomyia, Lophoceraomyia, and Oculeomyia of genus Culex, and three species belonging to subgenus Metalutzia of genus Lutzia are recognized in Thailand. Subgenus Oculeomyia includes a probable new species near Cx. infula and Lt. vorax is recognized as a new country record.