Centaurea cyanus, commonly known as cornflower or Bachelor’s-Button, is an annual flowering plant in the family Asteraceae, native to Europe. In the past it often grew as a weed in cornfields (in the broad sense of the word "corn", referring to grains, such as wheat, barley, rye, or oats), hence its name. It is also, through introduction as an ornamental plant in gardens and a seed contaminant in crop seeds, now naturalised in many other parts of the world, including North America and parts of Australia.
Cornflower is worldwide known for its color, named Cornflower blue t is a shade of medium-to-light blue. The most valuable blue sapphires are called cornflower blue, having a medium-dark violet-blue tone.