Greasers are a working class youth subculture that originated in the 1950s among young northeastern and southern United States street gangs. The style and subculture then became popular among other types of people, as an expression of rebellion.

In the 1950s and early 1960s, these youths were known as hoods. The name greaser came from their greased-back hairstyle, which involved combing back hair with wax, gel, creams, tonics or pomade. The term greaser reappeared in later decades as part of a revival of 1950s popular culture. One of the first manifestations of this revival was a 1971 American 7 Up television commercial that featured a 1950s greaser saying "Hey remember me? I'm the teen angel." The music act Sha Na Na also played a major role in the revival.

Although the greaser subculture was largely an American youth phenomenon, there were similar subcultures in the United Kingdom and Australia. The 1950s British equivalents were the ton-up boys, who evolved into the rockers in the 1960s. Members of rival subcultures in the UK, such as skinheads, sometimes referred to greasers simply as grease.