Bandeau (pl. bandeaux, diminutive of French bande, strip), a garment made of a strip of cloth. Today the term refers most frequently to the garment that wraps around a woman's breasts in sporting and bathing costumes dating back to Roman times. In the first half of the 20th century, "bandeaux" were also popular headdresses in the form of headache bands or headbands. The term is also used to refer to a wimple-like garment in the costumes of nuns, as well as of women of the medieval period.

In modern sporting and bathing costumes, a bandeau is a strapless garment worn around a woman's breasts. It may be fastened in the front or back or be sufficiently elastic so as to have no fastener at all. In a strict sense a bandeau has but two edges, although it is sometimes manufactured with a detachable halter strap that goes around the neck. A wide bandeau that covers much of the midriff is sometimes called a tube top.

As a silhouette the bandeau has been worn since Roman times. In the 1920s the term referred to a simply shaped brassiere, usually of a soft fabric and delicate trimmings providing little support or shaping. It was sometimes made from an elastic material to flatten or suppress the breasts in the style of the period. When the "boyish" silhouette went out of fashion, the word "brassiere" or later "bra" became the term for more shapely support garments.