genus of about 500 species of herbaceous plants of the composite family (Asteraceae). Most are native to the Old World and chiefly centred in the Mediterranean region.

The genus includes a wide variety of annual and perennial garden plants such as the cornflower (bachelor's button), or bachelor's button (C. cyanus), and the basket-flower (C. americana). Others are variously known as knapweed, thornless thistle, cardo-del-valle, dusty miller, blue bottle, mountain bluet, sweet-sultan, hard heads, and Spanish buttons.