Cleavage, anatomically known as the intramammary cleft or the intramammary sulcus, is the space between a woman's breasts lying over the sternum. Cleavage is exposed by garments with low necklines, including ball gowns, evening gowns, or swimwear.

Most people, both male and female, consider breasts an important aspect of femininity and many women use cleavage to enhance their physical and sexual attractiveness and to enhance their sense of femininity. Some people regard use of cleavage as a form of feminine flirting or seduction, within the confines of community, peer group and personal standards of modesty, as much as for its aesthetic or erotic effect. Some people derive erotic pleasure from seeing a woman's cleavage, some derive pleasure in their female partner exposing cleavage, and some women wear low-cut clothing for the pleasure of their partner. However, yet another group, such as those subject to gymnophobia, may feel uncomfortable with the sight of a woman's cleavage, or object to low-cut clothing for modesty or other reasons.