Male bra – also known as a compression bra, compression vest, or gynecomastia vest – refers to brassieres that are worn by men. Men sometimes develop breasts^[1][2] and the estimates of those with the condition are presented as a range "because the definition of gynecomastia varies and the method of surveying varies."^[3] Although there are options for treating gynecomastia,^[4] some elect surgery to reduce their breasts or wear a male bra.^[1] Male bras typically flatten rather than lift.^[5]

Men who choose to wear a brassiere may broadly be divided into two categories, depending on whether the brassiere is worn primarily for utilitarian purposes, or as a part of cross-dressing. Some men who have large breasts as a result of obesity or gynecomastia may choose to wear a brassiere to provide support for their breasts and to flatten their appearance. Other men wear bras for cross-dressing, for sexual purposes such as transvestic fetishism or feminization, or as a form of submission to their partner.^[6] Petticoat discipline may also involve male bra wear.^[7] Additionally, some male athletes – more specifically runners – may choose to wear a sports bra under their shirts in order to prevent a common medical condition called jogger's nipple, also known as nipple chafing. This condition is caused by excessive rubbing of wet sweat-soaked material over one's nipples. The condition, often very painful, can be prevented by wearing a sports bra.^[8][9]

Although some male bras have been developed, they often differ only superficially from bras designed for females.^[10][11] There is sometimes no medical necessity for men to wear bras, and the same considerations apply regardless of sex or gender.^[12]

In sports, a wearable device called a male bra is often used by sporting clubs to evaluate players with real-time statistics. It contains a tracking device (similar to a woman's sports bra with a heart rate monitor) that detects heart rate, distance traveled, fatigue, and other statistics that a coach can use to evaluate a player.^[13]

• In "The Doorman" episode of the TV sitcom Seinfeld, Kramer invents a male bra for Frank Costanza, who has large breasts. They disagree on the name, with Kramer wanting to call it a "bro" and Frank preferring "manssiere", a play on the term "brassiere".
• An episode of the American animated television sitcom Napoleon Dynamite titled "FFA", featured Napoleon revealing that he is wearing a "men's action bra" in a cutaway in which he competes in a "speed milking" contest.

• Breast fetishism
• Breast binding
• Breast reduction
• Klinefelter syndrome