A nightgown, nightie or nightdress is a loosely hanging item of nightwear, and is commonly worn by women and girls. A nightgown is made from cotton, silk, satin, or nylon and may be decorated with lace appliqués or embroidery at the bust and hem.

A nightgown may have any neckline, and may have sleeves of any type, or be sleeveless, and any shoulder strap or back style. The length of a nightgown may vary from hip-length to floor-length. A short nightgown can be called a "shortie" or a "babydoll", depending on the style. The sweep (taper from top to bottom) of the night gown can vary from virtually straight, to full circle sweep, like the Olga gown. A slip nightgown may be used as a nightgown or as a full slip. Nightgowns may be worn with a matching outer garment such as a robe, a sheer chiffon peignoir, or a dressing gown, to make them appropriate for receiving guests.