Cyclargus is a genus of butterflies in the family Lycaenidae. It was split off from the genus Hemiargus in 1948 by Vladimir Nabokov, although many lepidopterists have not accepted the new genus as valid. Nabokov designated C. ammon (Lucas's blue, from Cuba) as the type species for the genus, and included C. dominica (Jamaican blue, from Jamaica), C. thomasi (Thomas's blue, from Florida, the Bahamas, Puerto Rico and Hispaniola), C. woodruffi (from the Virgin Islands) and C. erembis (from the Cayman Islands, synonym of C. ammon erembis). In 1992 K. Johnston and Matusik described C. sorpresus and C. kathleena, both from Hispaniola.