A curtsy (also spelled curtsey or incorrectly as courtsey) is a traditional gendered gesture of greeting, in which a girl or woman bends her knees while bowing her head. In Western culture it is the feminine equivalent of bowing by males, and people will commonly curtsy in some churches as a simplified genuflection.

By the 17th and 18th centuries, it had become a standard social custom for women when greeting superiors, royalty, nobility, aristocracy or elders.

In more formal variants of the curtsy, the girl/woman bends the knees outward (rather than straight ahead), often sweeping one foot behind her. She may also use her hands to hold her skirt out from her body.

It is also acceptable in some cultures for the female to curtsy if wearing trousers or shorts.

The word "curtsy" is a phonological change from "courtesy" known in linguistics as syncope.

The origins of the curtsy can be traced back to royal court customs in Medieval Europe.

Courtly dance and etiquette manuals from the Renaissance describe movements of women dipping one knee and lowering the body that evolved into the curtsy. Italy and France under the Valois and later Bourbons were central in codifying this gesture.

By the Elizabethan era (1558–1603), court etiquette grew increasingly elaborate. While men were expected to perform deep bows or kneel in deference, women began adopting the curtsy as a gendered alternative, often assisted by the wide farthingale skirts which emphasized the downward motion. According to Desmond Morris, the motions involved in the curtsy and the bow were similar until the 17th century, and the sex differentiation between the actions developed afterwards. The earlier, combined version is still performed by Restoration comedy actors.