What revolutionary dress shape did Balenciaga introduce in 1957?

Balenciaga introduced the sack dress in 1957.

The sack dress was one of Cristóbal Balenciaga’s most radical experiments with silhouette. Instead of emphasizing the conventional waist and hourglass shape, it allowed the garment to hang more freely from the shoulders before narrowing toward the lower legs. The result appeared loose, modern, and deliberately detached from the body.

Its debut was part of Balenciaga’s broader postwar challenge to Christian Dior’s New Look, which had popularized a defined waist and full skirt from 1947 onward. Balenciaga repeatedly broadened shoulders, softened the waistline, and used sculptural volume to change how clothing related to the wearer’s body.

The sack dress is sometimes confused with Balenciaga’s tunic dress, introduced in 1955, or with the baby-doll dress, also associated with his late-1950s work. These were related innovations, but the 1957 sack dress is the canonical answer. The same period also produced his cocoon coat, balloon skirt, and high-waisted baby-doll dress.