A gay bar is a drinking establishment that caters to an exclusively or predominantly lesbian, gay, bisexual, and transgender (LGBT) clientele; the term gay is used as a broadly inclusive concept for LGBT and queer communities.

Gay bars once served as the centre of gay culture and were one of the few places people with same-sex orientations and gender-variant identities could openly socialize. Other names used to describe these establishments include boy bar, girl bar, gay club, gay pub, queer bar, lesbian bar, and dyke bar, depending on the niche communities that they served.