This paper presents a study of mafia groups in Bangladesh. Drawing on the views
and experiences of 22 street children, 80 interviews with criminal justice practitioners, NGO workers and community members and over 3 years of participant observation of the criminal justice system, the paper considers the ‘mastaans’: Bangladeshi mafia groups. The article draws on both theories of protection and behaviour to develop a social protection theory of the mafia. The article considers the social networks of mastaan groups, their prevalence, where they operate, divisions of labour, the crimes that they commit and the associations that they have with politicians and the police. The paper demonstrates that mastaans work in alliance with corrupt members of the state and they provide access to services, resolve disputes, commit extortion and carry out a wide array of criminal activity, much of which relies on their monopolisation of violence to protect their illegal industries. The paper demonstrates— for the first time—that mafias operate in Bangladesh and draws on data gathered from both adults and children, the implications of which are discussed.