Breast binding, also known as chest binding, is the flattening and hiding of breasts with constrictive materials such as cloth strips or purpose-built undergarments. Binders may also be used as alternatives to bras or for reasons of propriety.

Breast binding has been used in many historical contexts. Different time periods of history have had differing viewpoints on the female form, including the widespread use of corsets throughout western European history up to the Victorian era.

During the era of China's imperial dynasties, revealing the curves of a woman's breast was considered lewd and breasts were often bound with a moxiong or a dudou. The use of the garment was particularly popular during the Tang and Song dynasties. Breast binding became an exclusive aesthetic practice for women continuing until the 1930s, with more prevalence among upper-class women. The long-standing custom resulted from a culture that "believed large breasts were symbols of lasciviousness."

Korean women wearing the traditional hanbok concealed the female body by binding their breasts tightly with a cloth band.

In Japan, the traditional kimono flattens the appearance of the breasts, with breasts bound and flattened with an obi, and a datemaki belt wrapped around the torso from the chest to the waist. A sarashi is used by Japanese women to flatten their breasts.^{[citation needed]}

In Africa, adolescent Wodaabe girls had their breasts tightly bound to induce sagging, minimize sexual desirability, and improve their ability to breastfeed. In cultures where the breasts of pubescent girls are ironed to suppress their development, wealthier classes often choose to use an elastic belt to compress and flatten the breasts.

Until the early 20th century, many Catholic nuns bound their breasts under their habit to deflect the attention of male clergy and diminish sexual desire in men.

Breast binding was one of the punishments inflicted upon the women inmates confined in Ireland's Magdalene asylums.