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 stays, 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.