The sack-back gown or robe à la française was a women's fashion of 18th century Europe. At the beginning of the century, the sack-back gown was a very informal style of dress. At its most informal, it was unfitted both front and back and called a sacque, contouche, or robe battante. By the 1770s the sack-back gown was second only to court dress in its formality. This style of gown had fabric at the back arranged in box pleats which fell loose from the shoulder to the floor with a slight train. In front, the gown was open, showing off a decorative stomacher and petticoat. It would have been worn with a wide square hoop or panniers under the petticoat. Scalloped ruffles often trimmed elbow-length sleeves, which were worn with separate frills called engageantes.