Colias is a genus of butterflies in the family Pieridae. They are often called clouded yellows in the Palearctic and sulphurs in North America. The closest living relative is the genus Zerene, which is sometimes included in Colias.

The Pieridae are a large family of butterflies with about 76 genera containing about 1,100 species, mostly from tropical Africa and tropical Asia with some varieties in the more northern regions of North America and Eurasia. Most pierid butterflies are white, yellow, or orange in coloration, often with black spots. The pigments that give the distinct coloring to these butterflies are derived from waste products in the body and are a characteristic of this family. The family was created by William John Swainson in 1820.