A mannequin (also called a dummy, lay figure, or dress form) is a doll, often articulated, used by artists, tailors, dressmakers, window dressers and others, especially to display or fit clothing and show off different fabrics and textiles. Previously, the English term referred to human models and muses (a meaning which it still retains in French and other European languages); the meaning as a dummy dating from the start of World War II.

Life-sized mannequins with simulated airways are used in the teaching of first aid, CPR, and advanced airway management skills such as tracheal intubation. During the 1950s, mannequins were used in nuclear tests to help show the effects of nuclear weapons on humans. Also referred to as mannequins are the human figures used in computer simulation to model the behavior of the human body.

Mannequin comes from the French word mannequincode: fra promoted to code: fr , which had acquired the meaning "an artist's jointed model", which in turn came from the Flemish word mannekencode: nld promoted to code: nl , meaning "little man, figurine", referring to late Middle Ages practice in Flanders whereby public display of even women's clothes was performed by male pages (boys). Fashion shops in Paris ordered dolls in reed from Flemish merchants. Flanders was in logistics the easiest region to import dolls in reed from, as transport on the rivers Schelde and Oise provide easy routes from Flanders to Paris. As the Flemish wrote 'manneke(n)code: nld promoted to code: nl ' for 'little man' on their invoices, the Parisians pronounced this as 'mannequen', hence shifted to 'mannequin'. A mannequin is thus masculine, not feminine.