ABSTRACTInside a juvenile detention center in northeastern Brazil, inmates discussed and performed their manhood in compliance with a stereotyped local model of masculinity that equated manliness with aggression, fearlessness, and virility. But unlike the male subjects portrayed in recent anthropological studies of masculinity, these youths did not understand their manhood to be primarily configured in opposition to femininity. In fact, when adolescent detainees pronounced themselves to be men—or to be, as was more often the case, sujeito‐homens (man‐subjects)—they did so without reference to women, sexual activity, or sexual organs. Instead, they asserted their manhood by committing (or attempting to commit) murder: an act deliberately intended to deny the perpetrator's belonging to either the social or the legal category of the child. While juvenile justice professionals often interpreted such acts of aggression as expressions of innate criminal character, I argue that the murders and violent attacks that occurred in the juvenile detention center can be better understood as performative acts through which inmates sought to shore up and affirm their autonomy, accomplishments, and manhood in the face of juvenile justice laws and policies that refused to recognize them as anything but children. [violence, gender performativity, children, crime, masculinity]