A chaperone (also spelled chaperon) in its original social usage was a person who for propriety's sake accompanied an unmarried girl in public; usually she was an older married woman, and most commonly the girl's own mother.

In modern social usage, a chaperon (frequent in British spelling) or chaperone (usual in American spelling) is a responsible adult who accompanies and supervises young people. By extension, the word chaperone is used in clinical contexts.

Although the supervision of vulnerable women in public spaces may be common in many cultures, the specific word chaperon began to be used in the eighteenth century to denote a particular social institution, namely, a woman who would accompany a young unmarried woman in public, and especially where she might be expected to meet a man. In circumstances where, for whatever reason, the mother was unavailable to perform this function, another woman, usually well known to the family, was chosen. A chaperon was usually expected to be a married woman, although a respected, older unmarried or widowed woman (typically someone beyond child-bearing age) was often acceptable.

Chaperones were usually not required in situations where an unmarried woman's father was able to accompany his daughter(s). Chaperones for young men were not commonly employed in Western society until the latter half of the 20th century, although depending on the precise nature of the business he was on, a young male who temporarily left the company of his parents would usually find himself under the supervision of coaches, employers or other such individuals (such personnel were not typically seen to be chaperones in the traditional sense).