A stomacher is a decorated triangular panel that fills in the front opening of a woman's gown or bodice. The stomacher may be boned, as part of a corset, or may cover the triangular front of a corset. If simply decorative, the stomacher lies over the triangular front panel of the stays, being either stitched or pinned into place, or held in place by the lacings of the gown's bodice.
A stomacher may also be a piece or set of jewellery to ornament a stomacher or bodice.
In the 15th and 16th centuries, men and women both wore decorative stomachers (often called placards or plackets) with open-fronted doublets and gowns.
From about 1740, most gowns and bodices were worn to reveal the stomacher, which covered the front of the torso from neckline to waist or even below the waist. The bodice's lacings would then criss-cross over the stomacher, and eventually the lacings became a series of decorative bows.
Stomachers were often embroidered, or covered in pearls and other jewels. They could be made of the same fabric as the dress or of a contrasting fabric. Depending on the period, their bottom point was at waist level, or lower; towards the end of the 18th Century they could be as deep as 10 inches below the waistline, making it impossible for the woman wearing them to sit.
Necklines also defined the length of a stomacher. There was a brief period during the court of Louis XVI, when the neckline and stomacher actually were below the breasts, which were covered by a transparent ruffle of fabric called a fichu. The nipples could then be rouged or even pierced and decorated with pearls or other gemstones. This fashion did not take off, and, for the most part, the necklines ranged from demure to daring, but still covered the breasts.