What is a longline bra? A longline bra is a bra that extends to the waist or hips, almost like a corset. Unlike a corset, which has string or lace "stays" in the back that are tightened to achieve a certain "pulled in" waistline, a longline has a hook and eye back closure like a regular bra, except that it extends all the way down the back. A longline bra is used to achieve a smooth look underneath a dress or other outfit, and is often worn underneath bridal gowns, prom dresses, bridesmaid dresses or other formal wear. Because most of a bra's support comes from the band, a longline bra is extra supprotive and works great as a strapless bra alternative, especially for heavy breasts. Softcup or wirefree longlines are also great for improving posture and providing an extra comfortable support.