The Aryan Brotherhood is an American prison gang that only accepts Whites (although one of its more famous members, Michael Thompson, was part Native American), it is a neo-Nazi group with White supremacist leanings but tends to function much like any other gang - being involved in drug trafficking, extortion, inmate prostitution, and murder-for-hire.
Members of the Aryan Brotherhood often adorn themselves with Nazi symbols or Celtic designs (such as shamrocks) and although only making up a small number of the prison population are said to be involved in an unusually high percentage of prison murders.