Gull-wing door is an automotive industry term describing car doors that are hinged at the roof rather than the side, as pioneered by the 1952 Mercedes-Benz 300SL race car (W194) and its road-legal version (W198) introduced in 1954.

Opening upwards, the doors evoke the image of a seagull's wings. In French they are portes papillon (butterfly doors). The papillon door, slightly different in its architecture from a gullwing door – designed by Jean Bugatti in 1939 Type 64, fourteen years before Mercedes-Benz produced its similar, famous 300SL gullwing door – is a precursor, but is often overlooked when discussing "Gull-wing" design. Conventional car doors are typically hinged at the front-facing edge of the door and the door swings outward in a horizontal plane.