A sundress is an informal or casual dress intended to be worn in warm weather, typically in a lightweight fabric, most commonly cotton, and usually loose-fitting. It is commonly a bodice style, sleeveless dress, typically with a wide neckline and thin shoulder straps, and may be backless. A sundress is typically worn without a layering top and is not usually worn over a blouse, sweater or t-shirt, nor with leggings.

The sundress provides a feminine look that is more comfortable than a skirt and blouse or another sort of dress.

Sundresses can be of any neckline and hemline, ranging from mini to full length. It is typically sleeveless and collarless with a wide neckline and thin shoulder straps.