Bonnets are a variety of headgear for both sexes, which have in common only the absence of a brim.Bonnet derives from the same word in French, where it originally indicated a type of material. In the 21st century, only a few kinds of headgear are still referred to as bonnets, most commonly those worn by babies and Scottish soldiers.

The most common kind of bonnet worn today is a soft headcovering for babies. They are shaped similarly to the kind of bonnets women used to wear, that is they cover the hair and ears, but not the forehead. See also Coif.

In the mid-17th and 18th century "house bonnets" worn by women and girls were generally brimless headcoverings which were secured by tying under the chin, and which covered no part of the forehead. They were worn indoors, to keep the hair tidy, (illustration, left) and outdoors, to keep dust out of the hair. With hairstyles becoming increasingly elaborate after 1770, the "calash" bonnet was worn outdoors to protect the hair from wind and weather: a hood of silk or black taffeta stiffened with whalebone or arched cane battens, collapsible like a fan or the calash top of a carriage, they were fitted with ribbons to allow them to be held secure in a gale.

Headgear, headwear or headdress is the name given to any element of clothing which is worn on one's head.

Headgear serve a variety of purposes:

Bonnets, as worn by women and girls, were hats worn outdoors which were secured by tying under the chin, and often which had some kind of peak or visor. Some styles of bonnets had peaks so large that they effectively prevented women from looking right or left without turning their heads. Bonnets worn by men and boys are generally distinguished from hats by being soft and having no brim—this usage is now rare (they would normally be called caps today, except in Scotland where the "bunnet" is common in both civilian life and in the Royal Regiment of Scotland).

Caps are generally soft and often have no brim or just a peak (like on a baseball cap). For many centuries women wore a variety of head-coverings which were called caps. For example, in the 18th and 19th centuries a cap was a kind of head covering made of a flimsy fabric such as muslin; it was worn indoors or under a bonnet by married women, or older unmarried women who were "on the shelf" (e.g. mob-cap). An ochipok is part of traditional Ukrainian costume.