Colias is a genus of butterflies in the family Pieridae. They are usually called clouded yellows; the North American name "sulphurs" is elsewhere used for Coliadinae in general. The closest living relative is the genus Zerene, which is sometimes included in Colias. Notable lepidopterologists who did many studies on this genus included Julius Röber, J. Malcolm Fawcett, George B. Johnson and Henry Rowland-Brown.