Nightgown (also called a nightdress) is a loosely hanging item of nightwear nowadays solely for women. Its length may vary from hip-length (babydoll) to floor-length (peignoir) but is typically knee-length. A nightgown is manufactured of e.g. cotton, silk, satin, or nylon. It may be decorated with lace appliqu's or embroidery at cups and hem. Optionally, panties (UK - knickers) are worn under the nightgown (nightdress).
A short nightgown is often called nightie.
See also dressing gown and pyjamas.